How to redact a screenshot so the text cannot come back
Blurring or pixelating text does not reliably hide it, and a highlighter bar hides nothing at all. The safe way to redact a screenshot is to cover the sensitive parts with solid, opaque boxes, save the result as a new flat image, and then check the whole picture for other leaks.
Redact imageHide info in a screenshotOpenWhy blur and pixelation can be reversed
Blurring and pixelation both average neighbouring pixels. Averaging removes detail but leaves a pattern that depends on the original text. If someone knows the font, the size and the method used, they can generate candidate text, apply the same blur or pixelation to each candidate, and see which one matches. Published research has shown that pixelated text can often be recovered this way, especially when it is short and predictable, such as a number, a date or a name in a standard font.
The practical lesson is to treat blur and pixelation as decoration, not protection.
Why highlighter redactions fail
A highlighter in an editor is usually a semi-transparent colour placed over the text. The text is still in the picture, and the colour only tints it, so it can be read at normal size or with a contrast adjustment. The same problem exists with a black box drawn in a PDF viewer. The box covers the text on screen, but the text itself can remain in the file, so search, copy and selection may still reveal it.
Why a solid box on a flat image works
A solid, opaque box replaces the pixels under it with one colour, so nothing of the original letters is left in those pixels. The safe sequence has three parts:
- Draw solid boxes that cover the whole text, with some margin.
- Flatten the image or export it as a new PNG, so any layers merge into one picture. A box on its own layer can leave the text intact underneath.
- Open the new file to confirm the boxes are baked in.
| Method | Safe for text? | Why |
|---|---|---|
| Blur | No | The pattern survives and can be matched |
| Pixelation | No | Averaging keeps information |
| Semi-transparent highlight | No | The text is still visible underneath |
| Solid opaque box, flattened | Yes | The pixels are replaced with one colour |
Check for other leaks
A hidden name is often not the only thing that gives a person away. Before you send the file, look at:
- Browser tabs and bookmarks, which can show account names and sites
- Notification banners and message previews at the edges of the screen
- The address bar, which may contain account IDs, email addresses or search terms
- Window titles, taskbar or dock items and desktop icons
- Profile pictures, email addresses and contact names in chat sidebars
- Other windows peeking out from behind the main one
Then check the file itself. A screenshot usually has little metadata, but a photo of a screen can contain location data, so remove the location if the source was a photo. Finally, zoom in on the redacted areas and view the picture at a small size to see whether anything readable remains.
Redact a copy at full size
Do the work on a copy of the full-resolution screenshot, not on a file you have already shrunk or compressed, so the boxes sit exactly over the real text. Then export a new file for sharing. Keep the unredacted original somewhere private, so you can check later what was hidden.
What a careful redaction looks like
A good redaction covers each sensitive item completely, with a small margin, so no letter edge peeks out. It leaves enough of the picture to make the point you need, and it hides everything you do not intend to share. Box size can hint at how long the hidden text is, so cover a little more than the text itself.
Recognise a fake redaction
If you can select the text under a box, copy it, or see the text appear when you move the box in an editor, the redaction is not real. The same applies to a box that is only an annotation on a PDF, or a separate layer in an image editor. Export a flat image, or flatten the document, before you send it.
Quick answers
Can a blurred name be read again? Sometimes, partially, especially when the font and size are known and the text is short. Do not rely on blur for anything sensitive.
Is a highlighter a valid redaction? No. A semi-transparent highlight leaves the text visible underneath. Use a solid, opaque box on a flattened image.
Does a screenshot contain location data? Usually not, because screenshots rarely record a location. A photo of a screen can, so check where the picture came from.
