How to avoid constant Invalid Captcha error during IRCTC Tatkal ticket booking
Frustrated at getting "Invalid Captcha" error message repeatedly even after typing the correct Captcha during IRCTC Tatkal ticket booking? IRCTC limits the number of users trying to login during Tatkal hours by displaying a complicated Captcha image and giving "invalid captcha" error message. This article gives some tips & tricks to avoid the captcha error and login quickly. Follow these instructions and get a confirmed Tatkal train ticket.
What is Captcha ?
CAPTCHA stands for Completely Automated Public Turing Test to tell Computers and Humans Apart. It is a unique combination of alphabets and numbers displayed like a distorted image. Captcha is used in websites as a security measure to avoid spamming. Since the captcha image is unique and is different for each loading, an automatic computer program cannot identify and type it correctly and thus limit the access to only genuine users.Is irctc Captcha format different during tatkal hours ?
A CAPTCHA is displayed in the login page of IRCTC. User has to type the captcha correctly to log in to the website for ticket booking. There will be thousands of people trying to access the website during tatkal hours. Allowing them to login at the same time may lead to crash the website. Also, train tickets are issued at railway counters at the same time. If online tatkal booking is faster, then the chance of ticket availability for people in the long queue of railway booking counter will be less. To avoid this, IRCTC has limited the number of people access the website during the peak tatkal hours. One of these filtering methods is complicating the captcha so that there is less chance for user to enter it correctly. After tatkal hours, the captcha becomes normal and easy to read.
Captcha displayed during normal booking hours
Captcha displayed during tatkal booking hoursTatkal booking Time
IRCTC has some seats reserved in trains for emergency or immediate travel requirements. These are termed as tatkal reservation. Tatkal tickets can be booked one day in advance of the train starting day. That is, if a train starts on 3rd March and it reaches its destination on 4th, then, the tatkal booking will start on 2nd March. The time for tatkal train ticket booking is from 10 AM to 11 AM for AC tickets and 11 AM to 12 Noon for non AC tickets. Remember, no refund will be given to a confirmed tatkal ticket whereas a waitlisted tatkal ticket will be cancelled automatically and cash will be refunded to the account.How to book a tatkal ticket
Tatkal ticket is available only between 10 to 12 am on the previous day of the journey. It is very difficult to log into irctc website during tatkal hours unless you have a very high-speed Internet connection. So, it is safe to be logged in 5 minutes before the booking time starts. Don't be idle after logging in to the portal. The session will be expired automatically if the page is idle for more than 3 minutes. To avoid this, keep the session active by clicking / checking something in the page. Now irctc has limited the number of clicks per session. So, don't make too much enquiries and ticket availability checking just to keep the session active. If you exceed the number of permitted clicks also, your session will be expired. Keep all your details like passenger name, ID card number, mobile number, Credit/ debit card number etc. in a notepad so that you can just copy and paste them. The delay of even one second reduces the chance of ticket availability.How to type the correct Captcha in irctc website ?
The complexity of captcha shown during normal hours and tatkal hours are different. At regular ticket booking time, captcha will be easily readable. In tatkal time, it is shown in a wavy strikeout pattern, which is very difficult to read. There is 20% chance for it to get entered correctly. This is a traffic filtering technique adopted by the site. If you are not able to recognize the captcha correctly, try to refresh and get the new one immediately rather than trying your luck and wasting time. Another way to read the captcha easily is to Zoom in by pressing + button while holding Command key. You can make the page to the original size by pressing Command 0.
Software and plugins are available nowadays to bypass the captcha. But, it is safer to type the captcha manually, since these software may hack your important data. Keep all the above tips in mind while booking tatkal train tickets.

Crisp and brief, but very useful article.
I had faced the problem of difficult captcha during Tatkal hours and relative easiness at lean times . But I could not confirm the difference and was only a doubt with me. I was doubting it as deliberate attempts to delay genuine users and indirectly help vested interests. I thank the author to have cleared my doubt by this article.
The para with sub-heading"How to type the correct Captcha in irctc website ?" is especially useful and practically helpful.