Why image captchas are still everywhere
2026-10-02 · Captcha basics
Many portals still draw digits or a sum. The check is simple, and the picture is easy to explain.
Checkbox captchas and risk scores took over a lot of commercial websites. Walk through a government land record, a civic search, or a ticket form and you will often still see a small picture of digits, letters, or a one-line sum. That is a choice, not an accident.
The software is small. The server draws a string, stores it for a minute or two, and checks equality. There is no script from a third party in the page, no score to interpret, and no account with a captcha vendor. For a portal that already has a form and a session, a picture is an easy extra field.
The picture is also easy to explain to the person filling the form. "Type the digits" needs no instruction about browsers, cookies, or privacy policies. A Hindi-number sum uses a word a reader of Hindi already knows. The Hindi portal pattern is that one line.
These images did not freeze in 1997. Fonts got noisier, colours changed, and look-alike characters multiplied, because readers improved. The contract stayed the same: a file in, a short string out, a compare on the server. How captchas evolved puts that beside the checkbox generation.
That contract is the one Captcha OCR implements. Send the image. Read text when reliable is true. Refresh when it is not. A portal that has moved to a checkbox has left this contract, and the checkbox note is the one to read instead.
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