CAPTCHA (English Wikipedia)

Stec, Albert (12 June 2022). "What is CAPTCHA and How Does It Work?". Baeldung on Computer Science. Archived from the original on 1 November 2022. Retrieved 1 November 2022.

bbc.co.uk (Global: 11^th place; English: 10^th place)

"h2g2 – An Explanation of l33t Speak – Edited Entry". h2g2. 16 August 2002. Archived from the original on 6 September 2011.

berkeley.edu (Global: 621^st place; English: 429^th place)

cs.berkeley.edu

"Image Recognition CAPTCHAs" (PDF). UC Berkeley Department of Computer Science. Archived from the original (PDF) on 10 May 2013. Retrieved 28 September 2013.

boingboing.net (Global: 4,539^th place; English: 2,785^th place)

Doctorow, Cory (27 January 2004). "Solving and creating captchas with free porn". Boing Boing. Archived from the original on 9 February 2006. Retrieved 27 April 2015.

builtwith.com (Global: low place; English: low place)

trends.builtwith.com

"Websites using hCaptcha". trends.builtwith.com. Archived from the original on 10 November 2022. Retrieved 10 November 2022.

cloudflare.com (Global: low place; English: 8,037^th place)

cloudflare.com

"What is a CAPTCHA?". Cloudflare. 1 November 2022. Archived from the original on 27 October 2022. Retrieved 1 November 2022.
"How CAPTCHAs work | What does CAPTCHA mean?". Cloudflare. Archived from the original on 27 October 2022. Retrieved 27 October 2022.

blog.cloudflare.com

Meunier, Thibault (13 May 2021). "Humanity wastes about 500 years per day on CAPTCHAs. It's time to end this madness". Cloudflare blog. Based on our data, it takes a user on average 32 seconds to complete a CAPTCHA challenge.

cmu.edu (Global: 2,125^th place; English: 1,347^th place)

cylab.cmu.edu

"The reCAPTCHA Project – Carnegie Mellon University CyLab". www.cylab.cmu.edu. Archived from the original on 27 October 2017. Retrieved 13 January 2017.

ctftime.org (Global: low place; English: low place)

"CTFtime.org / #kksctf open 2019 / Kackers blockchained notes / Writeup". ctftime.org. Archived from the original on 27 October 2022. Retrieved 27 October 2022.

developers.google.com (Global: 3,679^th place; English: 7,859^th place)

"Invisible reCAPTCHA". Google Developers. Archived from the original on 16 January 2020. Retrieved 28 October 2022.

doi.org (Global: 2^nd place; English: 2^nd place)

von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (May 2003). "CAPTCHA: Using Hard AI Problems for Security" (PDF). Advances in Cryptology—EUROCRYPT 2003. EUROCRYPT 2003: International Conference on the Theory and Applications of Cryptographic Techniques. Lecture Notes in Computer Science. Vol. 2656. pp. 294–311. doi:10.1007/3-540-39200-9_18. ISBN 978-3-540-14039-9. Archived (PDF) from the original on 4 May 2019. Retrieved 30 August 2019.
Mayumi Takaya; Yusuke Tsuruta; Akihiro Yamamura (30 September 2013). "Reverse Turing Test using Touchscreens and CAPTCHA" (PDF). Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications. 4 (3): 41–57. doi:10.22667/JOWUA.2013.09.31.041. Archived (PDF) from the original on 22 August 2017.
Bursztein, Elie; Bethard, Steven; Fabry, Celine; Mitchell, John C.; Jurafsky, Dan (2010). "How Good Are Humans at Solving CAPTCHAs? A Large Scale Evaluation" (PDF). 2010 IEEE Symposium on Security and Privacy. pp. 399–413. doi:10.1109/SP.2010.31. ISBN 978-1-4244-6894-2. S2CID 14204454. Archived (PDF) from the original on 8 August 2018. Retrieved 30 March 2018.
Morreale, F.; Bahmanteymouri, E.; Burmester, B.; et al. (17 May 2023). "The unwitting labourer: extracting humanness in AI training". AI & Society. 39 (2024). Springer. 2392. doi:10.1007/s00146-023-01692-3. hdl:2292/64267. Retrieved 12 July 2026.
Feng, Yunhe; Cao, Qing; Qi, Hairong; Ruoti, Scott (June 2020). "SenCAPTCHA: A Mobile-First CAPTCHA Using Orientation Sensors". Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies. 4 (2). Article 43, pp. 1–26. doi:10.1145/3397312.
Sivakorn, Suphannee; Polakis, Iasonas; Keromytis, Angelos D. (March 2016). "I am Robot: (Deep) Learning to Break Semantic Image CAPTCHAs". 2016 IEEE European Symposium on Security and Privacy (EuroS&P). IEEE. pp. 388–403. Bibcode:2016eusp.conf...36S. doi:10.1109/EuroSP.2016.37. ISBN 978-1-5090-1751-5.
Karimi-Rouzbahani, Hamid; Bagheri, Nasour; Ebrahimpour, Reza (31 October 2017). "Invariant object recognition is a personalized selection of invariant features in humans, not simply explained by hierarchical feed-forward vision models". Scientific Reports. 7 (1): 14402. Bibcode:2017NatSR...714402K. doi:10.1038/s41598-017-13756-8. ISSN 2045-2322. PMC 5663844. PMID 29089520.
von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (2003). "CAPTCHA: Using Hard AI Problems for Security" (PDF). Advances in Cryptology—EUROCRYPT 2003. Lecture Notes in Computer Science. Vol. 2656. pp. 294–311. doi:10.1007/3-540-39200-9_18. ISBN 978-3-540-14039-9. S2CID 5658745. Archived (PDF) from the original on 4 May 2019. Retrieved 30 August 2019.
Moy, Gabriel; Jones, Nathan; Harkless, Curt; Potter, Randall (2004). Distortion estimation techniques in solving visual CAPTCHAs (PDF). Proceedings of the 2004 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. Vol. 2. IEEE. pp. 23–28. doi:10.1109/CVPR.2004.1315140. ISBN 978-0-7695-2158-9. Archived from the original (PDF) on 29 July 2020.
Bursztein, Elie; Beauxis, Romain; Perito, Hristo; Paskov, Daniele; fabry, Celine; Mitchell, John C. (2011). "The Failure of Noise-Based Non-continuous Audio Captchas". 2011 IEEE Symposium on Security and Privacy. pp. 19–31. doi:10.1109/SP.2011.14. ISBN 978-1-4577-0147-4. S2CID 6933726. Archived from the original on 16 April 2016. Retrieved 5 April 2016.
Gao, Song; Mohamed, Manar; Saxena, Nitesh; Zhang, Chengcui (23 June 2017). "Emerging-Image Motion CAPTCHAs: Vulnerabilities of Existing Designs, and Countermeasures". IEEE Transactions on Dependable and Secure Computing (Website). 16 (6) (1st ed.): 1040–1053. doi:10.1109/TDSC.2017.2719031. ISSN 1941-0018. S2CID 41097185.
"Yet Another Text Captcha Solver: A Generative Adversarial Network Based Approach" (PDF). 25th ACM Conference on Computer and Communications Security (CCS), 2018. doi:10.1145/3243734.3243754. S2CID 53106794. Archived (PDF) from the original on 29 October 2020. Retrieved 16 March 2020.

drive.google.com (Global: 900^th place; English: 800^th place)

"idrive turing patent application". Archived from the original on 15 March 2023. Retrieved 19 May 2017.
"idrive turing signup page". Google Drive. Archived from the original on 15 March 2023. Retrieved 19 May 2017.

duke.edu (Global: 1,851^st place; English: 1,041^st place)

cs.duke.edu

Moy, Gabriel; Jones, Nathan; Harkless, Curt; Potter, Randall (2004). Distortion estimation techniques in solving visual CAPTCHAs (PDF). Proceedings of the 2004 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. Vol. 2. IEEE. pp. 23–28. doi:10.1109/CVPR.2004.1315140. ISBN 978-0-7695-2158-9. Archived from the original (PDF) on 29 July 2020.

security.duke.edu

"Beyond CAPTCHAs: How Scammers Trick You Into Running Code". Duke Information Security. Duke University Security Offices. Retrieved 15 August 2025.

elie.net (Global: low place; English: low place)

Bursztein, Elie; Martin, Matthieu; Mitchell, John C. (2011). "Text-based CAPTCHA Strengths and Weaknesses". ACM Computer and Communication Security 2011 (CSS'2011). Archived from the original on 24 November 2015. Retrieved 5 April 2016.
Bursztein, Elie; Beauxis, Romain; Perito, Hristo; Paskov, Daniele; fabry, Celine; Mitchell, John C. (2011). "The Failure of Noise-Based Non-continuous Audio Captchas". 2011 IEEE Symposium on Security and Privacy. pp. 19–31. doi:10.1109/SP.2011.14. ISBN 978-1-4577-0147-4. S2CID 6933726. Archived from the original on 16 April 2016. Retrieved 5 April 2016.
Bursztein, Elie; Aigrain, Johnathan; Mosciki, Angelika; Michell, John C. (August 2014). The End is Nigh: Generic Solving of Text-based CAPTCHAs. WoOT 2014: Usenix Workshop on Offensive Security. Archived from the original on 16 April 2016. Retrieved 5 April 2016.

f5.com (Global: low place; English: low place)

"How Cybercriminals Bypass CAPTCHA". www.f5.com. Archived from the original on 27 October 2022. Retrieved 27 October 2022.

forbes.com (Global: 71^st place; English: 54^th place)

Hof, Robert. "AI Startup Vicarious Claims Milestone In Quest To Build A Brain: Cracking CAPTCHA". Forbes. Archived from the original on 15 September 2018. Retrieved 25 August 2017.

gizmodo.com (Global: 763^rd place; English: 486^th place)

Hurler, Kevin. "Chat-GPT Pretended to Be Blind and Tricked a Human Into Solving a CAPTCHA". Gizmodo. Archived from the original on 11 April 2023. Retrieved 11 April 2023.

googleblog.blogspot.com (Global: 6,935^th place; English: 8,461^st place)

"Teaching computers to read: Google acquires reCAPTCHA". Google Official Blog. Archived from the original on 31 August 2019. Retrieved 29 October 2018.

hcaptcha.com (Global: low place; English: low place)

"Who we are". www.hcaptcha.com. Archived from the original on 20 July 2023. Retrieved 20 July 2023. hCaptcha is a service of Intuition Machines.

hdl.handle.net (Global: 66^th place; English: 34^th place)

Morreale, F.; Bahmanteymouri, E.; Burmester, B.; et al. (17 May 2023). "The unwitting labourer: extracting humanness in AI training". AI & Society. 39 (2024). Springer. 2392. doi:10.1007/s00146-023-01692-3. hdl:2292/64267. Retrieved 12 July 2026.

heise.de (Global: 905^th place; English: 3,454^th place)

online, heise (10 May 2026). "Google's new reCAPTCHA: Potential hurdle for Google-free Android variants". heise online. Retrieved 15 July 2026.

infoq.com (Global: 9,906^th place; English: 7,884^th place)

Ghosemajumder, Shuman (8 December 2015). "The Imitation Game: The New Frontline of Security". InfoQ. InfoQ. Archived from the original on 23 March 2019. Retrieved 8 December 2015.

isyou.info (Global: low place; English: low place)

Mayumi Takaya; Yusuke Tsuruta; Akihiro Yamamura (30 September 2013). "Reverse Turing Test using Touchscreens and CAPTCHA" (PDF). Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications. 4 (3): 41–57. doi:10.22667/JOWUA.2013.09.31.041. Archived (PDF) from the original on 22 August 2017.

lancs.ac.uk (Global: low place; English: 8,918^th place)

eprints.lancs.ac.uk

"Yet Another Text Captcha Solver: A Generative Adversarial Network Based Approach" (PDF). 25th ACM Conference on Computer and Communications Security (CCS), 2018. doi:10.1145/3243734.3243754. S2CID 53106794. Archived (PDF) from the original on 29 October 2020. Retrieved 16 March 2020.

lifehacker.com (Global: 6,820^th place; English: 4,924^th place)

Long, Emily (17 June 2025). "Watch Out for Fake CAPTCHAs That Spread Malware". LifeHacker. Ziff Davis. Retrieved 15 August 2025.

lothar.com (Global: low place; English: low place)

petmail.lothar.com

"Hire People To Solve CAPTCHA Challenges". Petmail Design. 21 July 2005. Archived from the original on 18 September 2020. Retrieved 27 April 2015.

microsoft.com (Global: 263^rd place; English: 259^th place)

research.microsoft.com

Chellapilla, Kumar; Larson, Kevin; Simard, Patrice; Czerwinski, Mary. "Designing Human Friendly Human Interaction Proofs (HIPs)" (PDF). Microsoft Research. Archived from the original (PDF) on 10 April 2015.
"After 8 years of operation, Asirra is shutting down effective October 1, 2014. Thank you to all of our users!". Microsoft. Archived from the original on 7 February 2015.

microsoft.com

"Asirra is a human interactive proof that asks users to identify photos of cats and dogs". Microsoft. Archived from the original on 15 December 2008.
Elson, Jeremy; Douceur, John; Howell, Jon; Saul, Jared (October 2007). Asirra: A CAPTCHA that Exploits Interest-Aligned Manual Image Categorization. Proceedings of 14th ACM Conference on Computer and Communications Security. Microsoft. Archived from the original on 15 December 2008. Retrieved 15 September 2017.

nih.gov (Global: 5^th place; English: 5^th place)

ncbi.nlm.nih.gov

Karimi-Rouzbahani, Hamid; Bagheri, Nasour; Ebrahimpour, Reza (31 October 2017). "Invariant object recognition is a personalized selection of invariant features in humans, not simply explained by hierarchical feed-forward vision models". Scientific Reports. 7 (1): 14402. Bibcode:2017NatSR...714402K. doi:10.1038/s41598-017-13756-8. ISSN 2045-2322. PMC 5663844. PMID 29089520.

pubmed.ncbi.nlm.nih.gov

Karimi-Rouzbahani, Hamid; Bagheri, Nasour; Ebrahimpour, Reza (31 October 2017). "Invariant object recognition is a personalized selection of invariant features in humans, not simply explained by hierarchical feed-forward vision models". Scientific Reports. 7 (1): 14402. Bibcode:2017NatSR...714402K. doi:10.1038/s41598-017-13756-8. ISSN 2045-2322. PMC 5663844. PMID 29089520.

nytimes.com (Global: 7^th place; English: 7^th place)

Gugliotta, Guy (28 March 2011). "Deciphering Old Texts, One Woozy, Curvy Word at a Time". The New York Times. Archived from the original on 17 November 2017. Retrieved 29 October 2018.

patents.google.com (Global: 1,154^th place; English: 606^th place)

United States 6195698B1, Mark D. Lillibridge; Krishna Bharat & Martin Abadi et al., published 13 April 1998

pcworld.com (Global: 1,889^th place; English: 1,323^rd place)

Pippig, Laura (2 April 2025). "Watch out! Don't fall victim to these fake CAPTCHA scams on the web". PCWorld. PCWorld Communications. Retrieved 15 August 2025.

protectwebform.com (Global: low place; English: low place)

"Smart Captcha". Protect Web Form .COM. 8 October 2006. Archived from the original on 4 November 2016. Retrieved 15 September 2017.

prowebscraper.com (Global: low place; English: low place)

"Top 10 Captcha Solving Services Compared". Archived from the original on 15 December 2018. Retrieved 10 December 2018.

puremango.co.uk (Global: low place; English: low place)

Yeend, Howard (2005). "Breaking CAPTCHAs Without Using OCR". (pureMango.co.uk). Archived from the original on 25 June 2017. Retrieved 22 August 2006.

researchgate.net (Global: 96^th place; English: 89^th place)

Feng, Yunhe; Cao, Qing; Qi, Hairong; Ruoti, Scott (June 2020). "SenCAPTCHA: A Mobile-First CAPTCHA Using Orientation Sensors". Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies. 4 (2). Article 43, pp. 1–26. doi:10.1145/3397312.

semanticscholar.org (Global: 15^th place; English: 8^th place)

api.semanticscholar.org

Bursztein, Elie; Bethard, Steven; Fabry, Celine; Mitchell, John C.; Jurafsky, Dan (2010). "How Good Are Humans at Solving CAPTCHAs? A Large Scale Evaluation" (PDF). 2010 IEEE Symposium on Security and Privacy. pp. 399–413. doi:10.1109/SP.2010.31. ISBN 978-1-4244-6894-2. S2CID 14204454. Archived (PDF) from the original on 8 August 2018. Retrieved 30 March 2018.
von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (2003). "CAPTCHA: Using Hard AI Problems for Security" (PDF). Advances in Cryptology—EUROCRYPT 2003. Lecture Notes in Computer Science. Vol. 2656. pp. 294–311. doi:10.1007/3-540-39200-9_18. ISBN 978-3-540-14039-9. S2CID 5658745. Archived (PDF) from the original on 4 May 2019. Retrieved 30 August 2019.
Bursztein, Elie; Beauxis, Romain; Perito, Hristo; Paskov, Daniele; fabry, Celine; Mitchell, John C. (2011). "The Failure of Noise-Based Non-continuous Audio Captchas". 2011 IEEE Symposium on Security and Privacy. pp. 19–31. doi:10.1109/SP.2011.14. ISBN 978-1-4577-0147-4. S2CID 6933726. Archived from the original on 16 April 2016. Retrieved 5 April 2016.
Gao, Song; Mohamed, Manar; Saxena, Nitesh; Zhang, Chengcui (23 June 2017). "Emerging-Image Motion CAPTCHAs: Vulnerabilities of Existing Designs, and Countermeasures". IEEE Transactions on Dependable and Secure Computing (Website). 16 (6) (1st ed.): 1040–1053. doi:10.1109/TDSC.2017.2719031. ISSN 1941-0018. S2CID 41097185.
"Yet Another Text Captcha Solver: A Generative Adversarial Network Based Approach" (PDF). 25th ACM Conference on Computer and Communications Security (CCS), 2018. doi:10.1145/3243734.3243754. S2CID 53106794. Archived (PDF) from the original on 29 October 2020. Retrieved 16 March 2020.

springer.com (Global: 182^nd place; English: 172^nd place)

link.springer.com

von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (May 2003). "CAPTCHA: Using Hard AI Problems for Security" (PDF). Advances in Cryptology—EUROCRYPT 2003. EUROCRYPT 2003: International Conference on the Theory and Applications of Cryptographic Techniques. Lecture Notes in Computer Science. Vol. 2656. pp. 294–311. doi:10.1007/3-540-39200-9_18. ISBN 978-3-540-14039-9. Archived (PDF) from the original on 4 May 2019. Retrieved 30 August 2019.
Morreale, F.; Bahmanteymouri, E.; Burmester, B.; et al. (17 May 2023). "The unwitting labourer: extracting humanness in AI training". AI & Society. 39 (2024). Springer. 2392. doi:10.1007/s00146-023-01692-3. hdl:2292/64267. Retrieved 12 July 2026.
von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (2003). "CAPTCHA: Using Hard AI Problems for Security" (PDF). Advances in Cryptology—EUROCRYPT 2003. Lecture Notes in Computer Science. Vol. 2656. pp. 294–311. doi:10.1007/3-540-39200-9_18. ISBN 978-3-540-14039-9. S2CID 5658745. Archived (PDF) from the original on 4 May 2019. Retrieved 30 August 2019.

stanford.edu (Global: 194^th place; English: 182^nd place)

web.stanford.edu

Bursztein, Elie; Bethard, Steven; Fabry, Celine; Mitchell, John C.; Jurafsky, Dan (2010). "How Good Are Humans at Solving CAPTCHAs? A Large Scale Evaluation" (PDF). 2010 IEEE Symposium on Security and Privacy. pp. 399–413. doi:10.1109/SP.2010.31. ISBN 978-1-4244-6894-2. S2CID 14204454. Archived (PDF) from the original on 8 August 2018. Retrieved 30 March 2018.

infolab.stanford.edu

"Imagination Paper". Stanford University Infolab. Archived from the original on 2 October 2013. Retrieved 28 September 2013.

support.google.com (Global: 2,836^th place; English: 2,952^nd place)

"What is CAPTCHA?". Google Support. Google Inc. Archived from the original on 6 August 2020. Retrieved 9 September 2022. CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a [...]
"What is reCAPTCHA? –?reCAPTCHA Help". support.google.com. Archived from the original on 20 July 2023. Retrieved 20 July 2023.

thenextweb.com (Global: 2,998^th place; English: 2,466^th place)

Summers, Nick. "Vicarious claims its AI software can crack up to 90% of CAPTCHAs offered by Google, Yahoo and PayPal". TNW. Archived from the original on 15 September 2018. Retrieved 19 June 2018.

theskinny.co.uk (Global: 5,726^th place; English: 2,928^th place)

Shea, Michael (19 November 2015). "CAPTCHA: Spambots, eBooks and the Turing Test". The Skinny. Archived from the original on 27 January 2016. Retrieved 9 January 2016.

tipsmake.com (Global: low place; English: low place)

Soto, Micah (24 May 2019). "The origin of CAPTCHA and reCAPTCHA".

tripwire.com (Global: low place; English: low place)

"Making CAPTCHAs Expensive Again: If You're Using Text-Based CAPTCHAs, You're Doing It Wrong | Tripwire". www.tripwire.com. Archived from the original on 28 October 2022. Retrieved 28 October 2022.

tsts.com (Global: low place; English: low place)

Sulgrove, Jonathan (7 July 2022). "reCAPTCHA: What It Is and Why You Should Use It on Your Website – TSTS". Twin State Technical Services. Archived from the original on 10 November 2022. Retrieved 10 November 2022.

usenix.org (Global: 7,359^th place; English: 4,657^th place)

static.usenix.org

Motoyama, Marti; Levchenko, Kirill; Kanich, Chris; McCoy, Damon; Geoffrey, Voelker; Savage, Stefan (August 2010). Re: CAPTCHAs-Understanding CAPTCHA-Solving Services in an Economic Context.s (PDF). USENIX Security Symposium, 2010. Archived (PDF) from the original on 29 May 2016. Retrieved 5 April 2016.

w3.org (Global: 1,633^rd place; English: 1,401^st place)

May, Matt (23 November 2005). "Inaccessibility of CAPTCHA". W3C. Archived from the original on 21 May 2012. Retrieved 27 April 2015.
"Inaccessibility of CAPTCHA". www.w3.org. Archived from the original on 4 November 2020. Retrieved 31 October 2020.
"Inaccessibility of CAPTCHA". www.w3.org. Archived from the original on 27 October 2022. Retrieved 27 October 2022.

web.archive.org (Global: 1^st place; English: 1^st place)

"The reCAPTCHA Project – Carnegie Mellon University CyLab". www.cylab.cmu.edu. Archived from the original on 27 October 2017. Retrieved 13 January 2017.
von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (May 2003). "CAPTCHA: Using Hard AI Problems for Security" (PDF). Advances in Cryptology—EUROCRYPT 2003. EUROCRYPT 2003: International Conference on the Theory and Applications of Cryptographic Techniques. Lecture Notes in Computer Science. Vol. 2656. pp. 294–311. doi:10.1007/3-540-39200-9_18. ISBN 978-3-540-14039-9. Archived (PDF) from the original on 4 May 2019. Retrieved 30 August 2019.
"What is CAPTCHA?". Google Support. Google Inc. Archived from the original on 6 August 2020. Retrieved 9 September 2022. CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a [...]
Mayumi Takaya; Yusuke Tsuruta; Akihiro Yamamura (30 September 2013). "Reverse Turing Test using Touchscreens and CAPTCHA" (PDF). Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications. 4 (3): 41–57. doi:10.22667/JOWUA.2013.09.31.041. Archived (PDF) from the original on 22 August 2017.
"What is reCAPTCHA? –?reCAPTCHA Help". support.google.com. Archived from the original on 20 July 2023. Retrieved 20 July 2023.
Sulgrove, Jonathan (7 July 2022). "reCAPTCHA: What It Is and Why You Should Use It on Your Website – TSTS". Twin State Technical Services. Archived from the original on 10 November 2022. Retrieved 10 November 2022.
"Websites using hCaptcha". trends.builtwith.com. Archived from the original on 10 November 2022. Retrieved 10 November 2022.
"Who we are". www.hcaptcha.com. Archived from the original on 20 July 2023. Retrieved 20 July 2023. hCaptcha is a service of Intuition Machines.
Bursztein, Elie; Bethard, Steven; Fabry, Celine; Mitchell, John C.; Jurafsky, Dan (2010). "How Good Are Humans at Solving CAPTCHAs? A Large Scale Evaluation" (PDF). 2010 IEEE Symposium on Security and Privacy. pp. 399–413. doi:10.1109/SP.2010.31. ISBN 978-1-4244-6894-2. S2CID 14204454. Archived (PDF) from the original on 8 August 2018. Retrieved 30 March 2018.
Stec, Albert (12 June 2022). "What is CAPTCHA and How Does It Work?". Baeldung on Computer Science. Archived from the original on 1 November 2022. Retrieved 1 November 2022.
"What is a CAPTCHA?". Cloudflare. 1 November 2022. Archived from the original on 27 October 2022. Retrieved 1 November 2022.
Rodgers, Reece (3 November 2025). "The Curious Case of the Bizarre, Disappearing Captcha". WIRED. Archived from the original on 28 February 2026. Retrieved 12 July 2026.
"idrive turing patent application". Archived from the original on 15 March 2023. Retrieved 19 May 2017.
"h2g2 – An Explanation of l33t Speak – Edited Entry". h2g2. 16 August 2002. Archived from the original on 6 September 2011.
"idrive turing signup page". Google Drive. Archived from the original on 15 March 2023. Retrieved 19 May 2017.
"Teaching computers to read: Google acquires reCAPTCHA". Google Official Blog. Archived from the original on 31 August 2019. Retrieved 29 October 2018.
Gugliotta, Guy (28 March 2011). "Deciphering Old Texts, One Woozy, Curvy Word at a Time". The New York Times. Archived from the original on 17 November 2017. Retrieved 29 October 2018.
"How CAPTCHAs work | What does CAPTCHA mean?". Cloudflare. Archived from the original on 27 October 2022. Retrieved 27 October 2022.
Chellapilla, Kumar; Larson, Kevin; Simard, Patrice; Czerwinski, Mary. "Designing Human Friendly Human Interaction Proofs (HIPs)" (PDF). Microsoft Research. Archived from the original (PDF) on 10 April 2015.
"Making CAPTCHAs Expensive Again: If You're Using Text-Based CAPTCHAs, You're Doing It Wrong | Tripwire". www.tripwire.com. Archived from the original on 28 October 2022. Retrieved 28 October 2022.
Bursztein, Elie; Martin, Matthieu; Mitchell, John C. (2011). "Text-based CAPTCHA Strengths and Weaknesses". ACM Computer and Communication Security 2011 (CSS'2011). Archived from the original on 24 November 2015. Retrieved 5 April 2016.
von Ahn, Luis; Blum, Manuel; Hopper, Nicholas J.; Langford, John (2003). "CAPTCHA: Using Hard AI Problems for Security" (PDF). Advances in Cryptology—EUROCRYPT 2003. Lecture Notes in Computer Science. Vol. 2656. pp. 294–311. doi:10.1007/3-540-39200-9_18. ISBN 978-3-540-14039-9. S2CID 5658745. Archived (PDF) from the original on 4 May 2019. Retrieved 30 August 2019.
Moy, Gabriel; Jones, Nathan; Harkless, Curt; Potter, Randall (2004). Distortion estimation techniques in solving visual CAPTCHAs (PDF). Proceedings of the 2004 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. Vol. 2. IEEE. pp. 23–28. doi:10.1109/CVPR.2004.1315140. ISBN 978-0-7695-2158-9. Archived from the original (PDF) on 29 July 2020.
May, Matt (23 November 2005). "Inaccessibility of CAPTCHA". W3C. Archived from the original on 21 May 2012. Retrieved 27 April 2015.
Shea, Michael (19 November 2015). "CAPTCHA: Spambots, eBooks and the Turing Test". The Skinny. Archived from the original on 27 January 2016. Retrieved 9 January 2016.
"Inaccessibility of CAPTCHA". www.w3.org. Archived from the original on 4 November 2020. Retrieved 31 October 2020.
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Jakobsson, Markus (August 2012). The death of the Internet. Archived from the original on 15 October 2014. Retrieved 4 April 2016.
Ghosemajumder, Shuman (8 December 2015). "The Imitation Game: The New Frontline of Security". InfoQ. InfoQ. Archived from the original on 23 March 2019. Retrieved 8 December 2015.
Bursztein, Elie; Aigrain, Johnathan; Mosciki, Angelika; Michell, John C. (August 2014). The End is Nigh: Generic Solving of Text-based CAPTCHAs. WoOT 2014: Usenix Workshop on Offensive Security. Archived from the original on 16 April 2016. Retrieved 5 April 2016.
Summers, Nick. "Vicarious claims its AI software can crack up to 90% of CAPTCHAs offered by Google, Yahoo and PayPal". TNW. Archived from the original on 15 September 2018. Retrieved 19 June 2018.
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wiley.com (Global: 150^th place; English: 174^th place)

eu.wiley.com

Jakobsson, Markus (August 2012). The death of the Internet. Archived from the original on 15 October 2014. Retrieved 4 April 2016.

wired.com (Global: 254^th place; English: 178^th place)

Rodgers, Reece (3 November 2025). "The Curious Case of the Bizarre, Disappearing Captcha". WIRED. Archived from the original on 28 February 2026. Retrieved 12 July 2026.

worldcat.org (Global: 4^th place; English: 4^th place)

search.worldcat.org

Stringham, Edward P. (2015). Private Governance: creating order in economic and social life. Oxford University Press. p. 105. ISBN 978-0-19-936516-6. OCLC 5881934034.
Karimi-Rouzbahani, Hamid; Bagheri, Nasour; Ebrahimpour, Reza (31 October 2017). "Invariant object recognition is a personalized selection of invariant features in humans, not simply explained by hierarchical feed-forward vision models". Scientific Reports. 7 (1): 14402. Bibcode:2017NatSR...714402K. doi:10.1038/s41598-017-13756-8. ISSN 2045-2322. PMC 5663844. PMID 29089520.
Gao, Song; Mohamed, Manar; Saxena, Nitesh; Zhang, Chengcui (23 June 2017). "Emerging-Image Motion CAPTCHAs: Vulnerabilities of Existing Designs, and Countermeasures". IEEE Transactions on Dependable and Secure Computing (Website). 16 (6) (1st ed.): 1040–1053. doi:10.1109/TDSC.2017.2719031. ISSN 1941-0018. S2CID 41097185.

CAPTCHA (English Wikipedia)

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