Ryanair uses them, Ticketmaster uses them and even Expedia has been known to use them but Captchas are evolving from the squiggly often illegible words familiar to most.
That's no bad thing as an online user experience specialist recently described them as the 'most hated pieces of human interaction'.
Captchas are used to detect whether website visitors are humans or robots trawling for information such as pricing and availability.
In November, Ryanair changed from the Google-owned reCaptcha to a Solve Media solution that has also been used by Expedia, InterContinental Hotels Group and a number of US airlines in the past.
With the Solve Media solution users type in recognisable phrases such as 'sour grapes' above which the company claims are much easier to crack than the more traditional Captcha which can take a number of attempts.
The Solve Media system is also interesting because of the advertising/branding and even video footage it enables companies to put around the Captcha.
It is not the only company to try and address the problem with both game and image-based solutions now being used by companies.
Are You a Human, for example uses mini games, as above, for its Playthru human verification system and is also planning to offer branding opportunities around the system.
Chief marketing officer Ben Blackmer says these sorts of solutions are about improving the user experience and can improve form submissions by up to 50%.
He adds that part of the problem is that a lot of services in the market started like graduate projects and have suffered from a lack of investment.
"Nobody wants to have to prove their users are human, it's a necessary evil. My hunch is that people hate text based Captcha because it takes 2.5 times to complete and has a 75% success rate."
One other alternative Captcha system being touted is image based, where users click on a specific image where prompted, and companies including Confident Technologies offer this solution.
The company has also just released a mobile optimised version for use across smartphones and tablets.