Audio captchas
2026-10-11 · Captcha basics
An audio captcha is a sound clip for people who cannot see the picture. This API reads images only.
A visual captcha shuts out anyone who cannot see it. Sites added an audio alternative for that reason. The visitor presses a button, hears distorted speech or a string of spoken characters, and types what they heard. The server compares that text with the clip it generated, the same way it compares typed letters with a picture.
The clip is audio. It might be an MP3 or WAV behind a link. A picture of a speaker icon is not the sound. Sending that icon to an image reader produces a reading of the icon, which is useless as the answer.
Captcha OCR accepts images: PNG, JPEG, GIF, WebP, TIFF, BMP, and a restricted SVG. There is no audio field. What this API does not read states that in one line. If the portal offers both an image and an audio button, the image is the file you can send. The audio exists so a person can pass when the image is the wrong medium for them.
Captchas and accessibility is the wider point. A test that only a sighted person can pass was never a complete answer, which is why the audio button is there.
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