Anybody with a desktop browser can retype the words on a web page, screenshot the result, and send you the picture as proof. The edit changes the copy in their browser, without updating the site's files or records by itself. But the web address at the top of that picture stays real, and everything under it doesn't have to be.
On Windows and Linux, F12 opens the developer tools in Chrome, Firefox and Edge, and the Console is one of the tabs inside them. On a Mac it's Command-Option-I in those three browsers.
Type document.designMode = "on", hit Enter, and the page's ordinary text becomes editable. Select a headline, price or account balance written as text, then type over it. Numbers inside images or some app widgets won't change this way. The screenshot below shows a headline changed this way.
The edit stays on your screen
The setting changes your browser's copy of the page. On an ordinary page, it doesn't send the rewritten text back to the site. An app with its own editing or saving code may react to your typing, so don't assume all pages behave alike.
On a page that doesn't save the edits, reloading restores the original text. The screenshot still shows the fake.
The new words usually pick up the page's own typeface. Replacement text can change the spacing or wrapping, but some edits leave no obvious visual clue. Matching the number of letters doesn't guarantee a matching layout.
Checking the web address inside the picture won't catch this kind of fake. The address is genuine, because whoever faked it started from the genuine page.
Where the fakes turn up
Somebody sends a seller a picture of a payment that never happened. The seller ships the item and waits for money that never arrives.
ESET's security blog catalogues where faked screenshots turn up. Romance scams, where a screenshot of a booked flight explains a trip that never happens. Crypto group chats, where fake screenshots make an investment look like it's climbing.
A screenshot generally needs authentication before it's admitted as evidence in federal court. That means enough support to show it's what the person submitting it claims, not proof that everything in the picture is true.
Somebody with direct knowledge can testify to it. An expert witness, judge or jury can compare it with a record already shown to be genuine. Distinctive details in the picture, considered with the surrounding circumstances, can also help establish authenticity.
How to check one
Ask for the link and open it yourself. When money is involved, open your own bank or payment app instead of reading somebody else's picture of their app. A screen recording doesn't settle it, because the page stays editable while it's being filmed.
If a public page might be edited or deleted later, keep your own copy with Save Page Now. The Internet Archive fetches the page through its own servers, not through your browser, and stamps the copy with a date. Submitting a URL alone won't give the Archive access to pages that require your login, and some public sites block the Archive's crawler.
The designMode setting has dull uses too. Strip the clutter out of a page before you print it, or fix a typo in a mockup without touching the site's files. It was built for editing, and it doesn't care what you edit, or why.
