Captcha

What is a captcha?

A captcha is a test designed to tell humans apart from automated bots. The name is an acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart." It asks the visitor to do something easy for a person but hard for a script — read distorted text, select images, or simply tick a box that analyses behaviour in the background.

You'll most often meet captchas on forms, logins and checkout pages, where they stop automated abuse before it reaches the site.

What captchas protect against

• Spam: bots flooding contact and comment forms with junk submissions.
• Fake registrations: mass-created accounts used for fraud or abuse.
• Credential attacks: automated attempts to guess passwords at scale.
• Scraping and bulk actions: scripts harvesting data or abusing functionality.

Common types

• Text or image captchas: the classic distorted characters or "select all the traffic lights" grids.
• Checkbox (reCAPTCHA): a single "I'm not a robot" tick backed by behavioural analysis.
• Invisible / scoring: modern versions that run silently and only challenge suspicious visitors, keeping the experience frictionless.

Security vs user experience

Captchas are a trade-off: too aggressive and they frustrate real users and hurt conversion; too weak and bots get through. The current best practice favours invisible or low-friction options that protect the site without getting in the visitor's way — part of building a secure, well-maintained website. Get in touch if you need help protecting your forms.