How CAPTCHAs work | What does CAPTCHA mean?
What is a CAPTCHA?
A CAPTCHA test is designed to determine if an online user is really a human and not a bot. CAPTCHA is an acronym that stands for “Completely Automated Public Turing test to tell Computers and Humans Apart. ” Users often encounter CAPTCHA and reCAPTCHA tests on the Internet. Such tests are one way of managing bot activity, although the approach has its drawbacks.
Although CAPTCHAs are designed to block automated bots, CAPTCHAs are themselves automated. They’re programmed to pop up in certain places on a website, and they automatically pass or fail users.
How does a CAPTCHA work?
Classic CAPTCHAs, which are still in use on some web properties today, involve asking users to identify letters. The letters are distorted so that bots are not likely to be able to identify them. To pass the test, users have to interpret the distorted text, type the correct letters into a form field, and submit the form. If the letters don’t match, users are prompted to try again. Such tests are common in login forms, account signup forms, online polls, and e-commerce checkout pages.
The idea is that a computer program such as a bot will be unable to interpret the distorted letters, while a human being, who is used to seeing and interpreting letters in all kinds of contexts – different fonts, different handwritings, etc. – will usually be able to identify them.
The best that many bots will be able to do is input some random letters, making it statistically unlikely that they will pass the test. Thus, bots fail the test and are blocked from interacting with the website or application, while humans are able to continue using it like normal.
Advanced bots are able to use machine learning to identify these distorted letters, so these kinds of CAPTCHA tests are being replaced with more complex tests. Google reCAPTCHA has developed a number of other tests to sort out human users from bots.
What is reCAPTCHA?
reCAPTCHA is a free service Google offers as a replacement for traditional CAPTCHAs. reCAPTCHA technology was developed by researchers at Carnegie Mellon University, then acquired by Google in 2009.
reCAPTCHA is more advanced than the typical CAPTCHA tests. Like CAPTCHA, some reCAPTCHAs require users to enter images of text that computers have trouble deciphering. Unlike regular CAPTCHAs, reCAPTCHA sources the text from real-world images: pictures of street addresses, text from printed books, text from old newspapers, and so on.
Over time, Google has expanded the functionality of reCAPTCHA tests so that they no longer have to rely on the old style of identifying blurry or distorted text. Other types of reCAPTCHA tests include:
Image recognition
Checkbox
General user behavior assessment (no user interaction at all)
How does an image recognition reCAPTCHA test work?
For an image recognition reCAPTCHA test, typically users are presented with 9 or 16 square images. The images may all be from the same large image, or they may each be different. A user has to identify the images that contain certain objects, such as animals, trees, or street signs. If their response matches the responses from most other users who have submitted the same test, the answer is considered “correct” and the user passes the test.
Picking out certain objects from blurry photos is a hard problem for computers to solve. Even advanced artificial intelligence (AI) programs struggle with it – so a bot will struggle with it as well. However, a human user should be able to do this fairly easily, since humans are used to perceiving everyday objects in all kinds of contexts and situations.
How do reCAPTCHA tests with a single checkbox work?
Some reCAPTCHA tests simply prompt the user to check a box next to the statement, “I’m not a robot. ” However, the test is not the actual action of clicking the checkbox – it’s everything leading up to the checkbox click.
This reCAPTCHA test takes into account the movement of the user’s cursor as it approaches the checkbox. Even the most direct motion by a human has some amount of randomness on the microscopic level: tiny unconscious movements that bots can’t easily mimic. If the cursor’s movement contains some of this unpredictability, then the test decides that the user is probably legitimate. The reCAPTCHA also may assess the cookies stored by the browser on a user device and the device’s history in order to tell if the user is likely to be a bot.
If the test is still unable to determine whether or not the user is a human, it may present an additional challenge, such as the image recognition test described above. However, most of the time the user’s cursor movements, cookies, and device history are conclusive enough.
How does reCAPTCHA work without any user interaction?
The latest versions of reCAPTCHA are able to take a holistic look at a user’s behavior and history of interacting with content on the Internet. Most of the time, the program can decide based on those factors whether or not the user is a bot, without providing the user with a challenge to complete. If not, then the user will get a typical reCAPTCHA challenge.
What triggers a CAPTCHA test?
Some web properties just automatically have CAPTCHAs in place as a proactive defense against bots. Other times, a test may be triggered if user behavior seems to resemble a bot’s behavior: if users request webpages or click hyperlinks at a far higher rate than average, for instance.
Are CAPTCHAs and reCAPTCHAs enough for stopping malicious bots?
Some bots can get past the text CAPTCHAs on their own. Researchers have demonstrated ways to write a program that beats the image recognition CAPTCHAs as well. In addition, attackers can use click farms to beat the tests: thousands of low-paid workers solving CAPTCHAs on behalf of bots.
Besides a CAPTCHA, there need to be other strategies in place for stopping unwanted bots (such as content scraping bots, credential stuffing bots, or spam bots).
What are the drawbacks of using CAPTCHAs or reCAPTCHAs to stop bots?
Bad user experience: A CAPTCHA test can interrupt the flow of what users are trying to do, giving them a negative view of their experience on the web property, and leading to them abandoning the webpage altogether in some cases.
Not usable for visually impaired individuals: The problem with CAPTCHAs is that they rely on visual perception. This makes them nearly impossible, not just for people who are legally blind, but for anyone with seriously impaired vision.
These tests can be fooled by bots: As described above, CAPTCHAs are not fully bot-proof and shouldn’t be relied upon for bot management.
Are there alternatives to using CAPTCHAs or reCAPTCHAs?
Bot management solutions such as Cloudflare Bot Management or Super Bot Fight Mode can identify bad bots without impacting the user experience, based on the behavior of the bot. This way, bots can be mitigated without forcing users to complete CAPTCHAs.
How are CAPTCHA and reCAPTCHA related to artificial intelligence (AI) projects?
As millions of users identify hard-to-read text and pick out objects in blurry images, that data is fed into AI computer programs so that they become better at those tasks as well.
In general, computer programs struggle with identifying objects and letters in different contexts, because context can change almost infinitely in the real world. For instance, a stop sign is a red octagon with white letters reading “STOP. ” A computer program could identify a shape-and-word combination like that fairly easily. However, a stop sign in a photo may look very different from that simple description depending on context: the angle of the photo, the lighting, the weather involved, and so on.
Via machine learning, AI programs can get better at overcoming these limitations. For the stop sign example, the programmer would feed the AI program a bunch of data on what is and is not a stop sign. For this to be effective, they need lots of examples of images with stop signs and images without stop signs, and they need human users to identify them until the program has enough data to be effective at it.
reCAPTCHA helps fill this need by getting humans to identify objects and texts, which slowly provides enough data to build robust AI programs.
What is a Turing test? How are Turing tests relevant to CAPTCHA tests?
A Turing test assesses a computer’s ability to mimic human behavior. Alan Turing, an early computing pioneer, invented the concept of a Turing test in 1950. A computer program “passes” the Turing test if its performance during the test is indistinguishable from that of a human – if it acts the way that a human would act. A Turing test is not dependent on getting answers correct; it’s about how “human” the answers sound, regardless of whether they’re right or wrong.
Although it’s called a “Public Turing test, ” a CAPTCHA is really the opposite of a Turing test – it determines whether a supposedly human user is actually a computer program (a bot) or not, instead of trying to determine if a computer is human. To accomplish this, a CAPTCHA needs to assign a brief task that people tend to be good at and computers struggle with. Identifying text and images usually fits those criteria.
Why can’t bots read Captchas?: askscience – Reddit
In short: Captchas are designed to be unreadable for machines, hence bots shouldn’t be able to read theb (but they are gettin better at it). Programs that transform images into text face the problem that they get is in essence a big grid of color values. It says “well, pixel (x, y) is pretty black, pixel (x+1, y) is kindof grey… ” and so on. It isn’t possible for the computer to look at the whole image as a human does. Instead it traces pixels that border on other pixels which have a large difference in color. This way it detects edges give you some shape you can work with, for example, you might get four lines, one is a long vertical one, the other three are horizontal and shorter. Two of these intersect the vertical one, while one doesn’t connect. Using some kind of pattern recognition your program could recognize this as an ‘E’. However you have to account for small errors that occur during edge detection. This works well enough (but not perfectly) if you give the program a nice scan of a black and white, printed run into problems pretty quickly when you encounter low resolution scans, skewed lines or worse, handwriting. The latter is especially difficult to recognize, since letters aren’t uniform. Some methods that work are programs that simulate neural networks, that can learn how to read a specific handwriting with some ptchas try to distort text in such a way that computers cannot recognize it, by advertently introducing the problems I’ve mentioned above. For example, if you take a text like “Foo” and run a horizontal black line below the text and a vertical white line through one of the ‘o’s, the program will probably be trown off course and read something like “Eeo”. Most of the time humans can read it, but somtimes even we fail. That shows us how good these captcha-bots have cause bots are getting better at reading texts, captchas are moving away from text to things that are much harder to do on a computer. For example challenges such as “find the animal that is not a cat” while presenting you eight dogs and one cat. Easy for a human but very difficult for a machine.
Fix I’m Not A Robot reCAPTCHA Issue in Google Search – WebNots
CAPTCHA is an acronym for Completely Automated Public Turing test to tell Computers and Humans Apart. This is a challenging test to differentiate between humans and automated bots based on the response. reCAPTCHA is one of the CAPTCHA spam protection services bought by Google. Now it is being offered for free to webmasters and Google also uses the reCAPTCHA on their own services like Google Search.
Automated robots are the biggest headache for producing spams and consuming server resources which supposed to be utilized by real users. In order to avoid automated bots Google introduced “No CAPTCHA reCAPTCHA” API concept for website owners to protect their sites. Later to improve user experience, Google introduced invisible reCAPTCHA and also Android API.
Invisible CAPTCHA helps to stop bots without showing “I’m not a robot” message to human users. But it does not work on many situation as the message will be still shown. For example, Google search page itself will show the “I’m not a robot” CAPTCHA message on certain circumstances when you enter the query and hit search button. You will be asked to prove you are a human by selecting the checkbox or selecting images based on the given hint.
Why This is Embarrassing?
When you do a real Google search and getting interrupted with “I’m not a robot” message will make you really embarrassing. Sometimes it will allow you with a simple click on the checkbox. Google will check the clicking position on the checkbox. Bots click exactly on the center of the checkbox while humans click somewhere on the box. This will help to decide Google whether the user is a human or bot.
Google Search CAPTCHA Verification
Even there is a browser extension for Chrome to click on the checkbox as soon as the page loads.
But most of the time it needs you to verify five or six times before seeing the real search results. Remember to click the “Verify” button when you do not see the matching images or when you feel the verification is done. Google will decide to confirm the verification or still continue to verify further.
Annoying Image Verification
In the worst case, Google will completely stop you by showing the sorry page. The only option you have here is to wait and try later.
Google Sorry Page
What is the Root Cause of I’m Not a Robot reCAPTCHA Message?
Well, when you get the “I’m not a robot” reCAPTCHA message, just click on the “Why did this happen? Link. Alternatively you can go to this sorry page of Google anytime to see the reasons as below:
This page appears when Google automatically detects requests coming from your computer network which appear to be in violation of the Terms of Service. The block will expire shortly after those requests traffic may have been sent by malicious software, a browser plug-in, or a script that sends automated requests. If you share your network connection, ask your administrator for help — a different computer using the same IP address may be responsible. Learn moreSometimes you may see this page if you are using advanced terms that robots are known to use, or sending requests very quickly.
Fix I’m Not A Robot reCAPTCHA Issue in Google Search
Now you know why it happens!!! If you are always getting interrupted then here are some tips to fix I’m not a robot issue in Google search.
Check your IP addressCheck your networkStop using VPNAvoid unknown proxy serversUse Google public DNSStop searching illegal queriesSlow your clicksStop sending automated queriesSearch like a humanCheck for malware and browser extensions
Unfortunately there are no strong alternatives to Google search. Bing and Yahoo! are far away from the expected results and no where nearer to the accuracy of Google. So, try out the below options to fix i’m not a robot problem, even some points don’t make correct sense to you.
1. Check Your IP Address
Google blocks the search results based on the originating IP address. There are large numbers of databases maintained publicly and by private companies to keep track of the suspicious IP addresses. If there are any suspicious activities from your IP address and is marked for spam then Google will throw the reCAPTCHA message and stop you for verification.
Generally internet service providers use dynamic IP addresses with large range. So disconnect the internet connection and reconnect to get the new IP address. Or just wait for sometime then try searching again. Possibly you can reset your modem or router connection for this. Follow the below steps if you want to reset the IP address manually:
Reset IP Address on Windows 10:
Press “Windows + X” keys to open power user menu and go to ““Command Prompt (Admin)” the following commands to reset the network adapter and IP address.
netsh winsock resetnetsh int ip resetipconfig /releaseipconfig /renew
Reset IP Address on Mac:
Press “Command + Spacer bar” to open spotlight search and go to “System Preferences” to “Network” options and choose your active Wi-Fi “Click the lock to make changes” and enable the edit mode by providing your administrator to “Advanced…” option and then “TCP/IP” on the “Renew DCHP Lease” to release and renew your IP address.
Reset IP in Mac
2. Check Your Network
Sometimes (mostly in countries like China) the Internet Service Provider (ISP) masks the IP address and track your browsing activities. This will cause the complete network of IP addresses used by that ISP to get blocked by security systems like reCAPTCHA used by Google. If you face the CAPTCHA on every instance then approach your ISP and clarify with them on the issue.
The other network issue could be due to sharing of WiFi network. In this case there are possibilities someone else on your network might be sending some automated traffic and Google will stop the searches from the entire network. You can contact the network administrator to address the issue and get more details.
Also you can get an unique static IP for you from your ISP. This will help you to overcome the spammy network problem. Learn more on how to assign a static IP address to your computer.
3. Stop Using VPN
Virtual Private Network (or VPN) hides your IP address and route the traffic from different location. This is used to access the blocked websites and also used mainly for hiding the originating IP address to do illegal activities. Use of VPN is illegal in many countries due to the nature of usage. Though you may use for good purposes, the entire server may not be clean or blocklisted.
Therefore, avoid using free VPN applications and uninstall them from your computer. If you are using premium VPN service, discuss with your VPN service provider and get the appropriate server to connect properly. As far as we have checked, most of the time Google shows i’m not a robot reCAPTCHA verification when connecting through VPN server. The problem rarely occurs when disconnected from VPN and using Google public DNS.
4. Avoid Unknown Proxy Servers
Similar to ISP and VPN, the proxy server you use can also cause you the trouble as illegal activities might be identified through that proxy server. Don’t use unreliable proxy servers on your browser to route all traffic through them. On Windows 10, you can press windows key and go to “Settings > Network & Internet” option. Here you can disable all proxy and VPN connections. Learn more about changing network settings in Windows.
On Mac, follow the similar steps as explained above for resetting IP address. Under “Proxies” tab, ensure to remove all proxy servers.
5. Use Google Public DNS
Another problem in the network could be your DNS. Domain Name System or DNS helps to resolve numeric IP address of a website to a host name. The DNS problem could be from your computer settings or from the ISP’s or from the VPN’s private DNS. Though corrupted DNS will not cause reCAPTCHA message it will slow down the connection.
The simple solution here is to switch the DNS to reliable public DNS. Check out the article on how to use Google public DNS. In most of the cases, this will work out to overcome internet connection problems.
6. Stop Searching Illegal Queries
Well, if you are really trying to search illegal terms then most probably Google will stop you for verification. You can clear your browser’s cache and try searching again. Remember Google can easily track all search queries from the IP addresses. So clearing browser’s cache will work only if you accidentally searched something wrong. Otherwise any searches violating Google terms will get stopped and you should wait sometime before retrying.
7. Slowdown Your Clicks
If you are not using VPN, proxy and your IP and ISP are good then the most probable cause could be the unusual clicks from you. When you enter the keyword and hit the enter key very fast, Google will match your activity with the automated bots and stop you.
Though this is strange, slowdown your mouse clicks and speed and use normal speed to avoid the CAPTCHA message.
8. Stop Sending Automated Queries
You can easily search terms directly using the URL like “. This is the most popular way automated bots send traffic to Google. Always use the search box to send the query terms and avoid searching directly with the URL.
If you are a developer, stop manipulating the user query before sending to Google. Also display the search results as it obtained from Google without manipulating.
9. Search Like Human Not Robots
Again, this may embarrass you!!! But there are lot of differences between the search behaviors of humans and automated robots. Especially when you are already signed in with your Google account, it is easy for Google to understand you are human. But this is not sufficient as the network problems can take more precedence than the browsing history of the account.
For example automated bots use the capital letters in-between the words while most humans will not search like that. So always search the term using the way normal humans do.
10. Check Malware & Browser Extensions
Your computer may be infected with malware that sends automated traffic to Google. Also some browser extensions and plugins can send automated traffic. If you are frequently seeing “I’m not a robot” message then check your computer for malicious programs and remove unnecessary browser extensions. Try the official Chrome cleanup tool if you use Chrome and Windows operating system.
If you have removed any malware then reset the browser settings to initial settings.
Final Thoughts
Google will only stop with CAPTCHA message when there are unusual traffic activities detected. Once the unusual activity is stopped Google will allow you to search normally. So if you are seeing the message frequently then definitely there is something wrong. Most probably the network is spammy or you are too fast matching the bots. Consider thoroughly checking your network, slow down your activities and use public DNS to get rid of the “I’m not a robot” CAPTCHA message. If you still have a problem then post your issue in official Google search forum to get advise from experts.
Frequently Asked Questions about robot passes captcha
Can robots solve CAPTCHA?
Some bots can get past the text CAPTCHAs on their own. Researchers have demonstrated ways to write a program that beats the image recognition CAPTCHAs as well. In addition, attackers can use click farms to beat the tests: thousands of low-paid workers solving CAPTCHAs on behalf of bots.
Why can robots not pass CAPTCHA?
In short: Captchas are designed to be unreadable for machines, hence bots shouldn’t be able to read theb (but they are gettin better at it). Programs that transform images into text face the problem that they get is in essence a big grid of color values.
How do I stop I am not a robot CAPTCHA?
If you are always getting interrupted then here are some tips to fix I’m not a robot issue in Google search.Check your IP address.Check your network.Stop using VPN.Avoid unknown proxy servers.Use Google public DNS.Stop searching illegal queries.Slow your clicks.Stop sending automated queries.More items…•Mar 29, 2021