Free photo tools/Cover or pixelate part of a photo

How to redact a screenshot before you share it

Cover each private part with a solid, fully opaque box, save the result as a new flat picture, and look at the saved file before you send it. A solid box replaces the pixels. A see-through marker, a blur, or pixelation leaves a trace of the text in the picture.

By Paul Bădărău, maker of Milkglass. Written on 7 October 2026.

The steps

1. Open the photo redactor in your browser, on the phone or on the computer.
2. Choose the screenshot, or drop it on the frame.
3. Drag a box over each part to hide. Keep Solid cover selected.
4. Move a box by dragging it, and resize it by a corner. Make each box a little larger than the text.
5. Select Save the covered photo and download the file. It has the name of the original with -redacted added.
6. Open the saved file, look at it once, and send that file.

A screenshot is usually a PNG file, and the tool saves a PNG as a PNG. That format stores every pixel exactly. The text that you left visible stays as sharp as it was, and every pixel inside a box is black.

What to cover in a screenshot

A screenshot holds more than the part you wanted to show. Go through it from top to bottom:

• The status bar. The time, the carrier, and the battery level.
• The top of the app. The name or the number of the person in a chat, your own account name, the address bar of the browser, the titles of other tabs.
• The content. Names, phone numbers, email addresses, order and customer numbers, amounts, addresses, faces in profile pictures.
• What slid in. A notification banner with the first line of another message.
• The bottom. The keyboard with a half-typed text and its suggestions.

The same fact often appears twice: a name in the header and again in the first message, an order number in the title and again in the text. Cover both.

Cover the whole word, and a little more

A box that follows a word exactly tells how long the word is. In a chat with four people, the length of a name can be enough to pick the person. When the line is the secret, cover the full line, from one edge of the bubble to the other. For a number, cover all of it and not only the last digits.

Why the marker of your phone is a risk

The drawing tools of a screenshot editor are made for notes, and several of them are see-through by design. The Markup tools of the iPhone have an opacity setting: Apple's guide Use Markup on your iPhone says to tap a selected tool again to change the opacity of its color. A stroke with less than full opacity darkens the text and keeps it. In 2018, 9to5Mac showed that text under coats of the Markup marker came back when the picture was lightened in a photo editor.

If you use a drawing tool, pick the pen, set the opacity to full, and draw until no gap is left. A solid box does the same with one drag.

Why blur and pixelation are a risk for text

Both compute the new pixels from the old ones. The result still depends on the letters, and a program can test guesses against it. Researchers showed this for blurred and mosaiced text in 2016 (Hill and others), and a public tool for pixelated text followed in 2022 (Bishop Fox). The guide Is pixelation safe for hiding text? explains how it works.

A crop can keep what you cut

Cropping is fine for the edge of a screenshot, with one lesson from 2023. A flaw in the screenshot editor of Google Pixel phones, known as aCropalypse (CVE-2023-21036), left the cut-off part of the picture in the saved file, and a large part of the original could be brought back from it. Google fixed the flaw in March 2023 (Malwarebytes).

The lesson holds for every tool: what counts is the file that you send, not the picture that the editor shows. The redactor on this site draws a new picture and writes a new file that holds that picture, with a color profile where the browser writes one. It then reads the file back and offers the download only when the file holds no metadata.

Check the file before you send it

• Open the saved file, not the editor, and zoom in on each box.
• Read the picture once as the receiver would. What can you still learn from it?
• Look at the name of the file. A name such as "chat with Anna.png" tells what the box hides. Rename it.
• Send the saved copy, and keep the original to yourself.