TidyToolsWhy the obvious tools aren't safe
The instinct is to open the screenshot in Preview, Paint or a PDF annotator and draw a black rectangle over the sensitive part. In a plain image editor that usually works, because the picture has no layers and the rectangle really does overwrite the pixels. In almost anything else, it doesn't.
Annotation tools, PDF markup, Word, PowerPoint and most note apps store the rectangle as an object sitting on top of the image. The picture underneath is unchanged and complete. Anyone who opens the file can select the black box and move or delete it, and what was underneath is right there. This is not a hypothetical: it is how unredacted names, addresses and case details have repeatedly reached the public through documents their authors believed they had censored.
This tool has no layers to get wrong. Each box is painted directly into the picture, and the file you download is a flat image built from the result. There is nothing on top of anything.
Blurring and pixelating are worse than they look
Pixelation feels safer than a black bar because you can still see something — which is exactly the problem. A pixelated block is a deterministic summary of what was underneath: each square is the average of the pixels it replaced. That is information, and for text it is often enough information to reverse.
The attack is straightforward. Text on a screen uses a known font at a known size, so an attacker can render every candidate string, pixelate each one the same way, and compare. Short, structured, guessable strings — names, usernames, account numbers, postcodes, amounts — fall quickly. Public tools that do this have existed for years. Swirl and mosaic filters have the same weakness, and heavy Gaussian blur is better but still leaks the shape and length of what it hides.
A solid bar leaks nothing at all, because there is nothing left to analyse. That's why this tool only offers solid bars, and why it's worth resisting the prettier option.
A worked example
You want to post a screenshot of a bank app showing a confusing charge. Visible in the frame: your name at the top, the account number, your balance, and two other transactions that are nobody's business.
Drop it in, drag a box over each of the four, and download. The result is a PNG where those regions are solid black — and if anyone opens it in an editor there is no rectangle to move, because there is no rectangle. There is just an image with black areas in it.
The metadata goes too
A useful side effect: because the redacted copy is rebuilt from scratch rather than edited in place, everything that isn't picture is dropped. Any capture timestamp, device details or software identifiers in the original file are simply not present in the new one.
That matters more for photographs than screenshots — a photo of a screen can carry the camera and GPS coordinates of where you took it. If you want to see what a file is carrying before you share it, the photo metadata viewer shows all of it.
What this still can't do for you
- It can't find things for you. Every box is one you drew. Check the edges, the browser tab titles, the notification bar, the reflection in a window, and the file name itself before you share.
- It can't help once the original is out. Redact before posting; a deleted post is not an unsent one.
- It doesn't shrink the frame. If the sensitive material is at the edge, cropping it away is cleaner than covering it.
Frequently asked questions
Is my screenshot uploaded anywhere?
No. The image is drawn and redacted inside this page and saved straight to your downloads. There is no server, no account and nothing stored. Load the page, disconnect from the internet, and it still works — which for this tool in particular is the only claim worth making.
Can the black bars be removed from the downloaded file?
No. They aren't objects placed over the image — the pixels underneath are overwritten before the file is written, so there is nothing beneath them to uncover.
Why is there no blur or pixelate option?
Because for text they are not safe. A pixelated block is an average of what it replaced, and short predictable strings can be recovered by rendering candidates and matching them. A solid bar leaves nothing to analyse.
Does it work on a phone?
Yes — drag with your finger to draw each box. It's often easier to redact on the device the screenshot was taken on, before it's been copied anywhere else.
Does redacting reduce the image quality?
Saving as PNG is lossless, so everything outside the bars is pixel-for-pixel identical. JPG re-encodes and loses a little, so PNG is the default and the better choice for screenshots of text.
Does it remove the metadata as well?
Yes, as a side effect of rebuilding the image. Timestamps, device details and any location data in the original are not carried into the redacted copy.
Can I redact a PDF this way?
Not here — this works on images. For a PDF the reliable approach is to remove the whole page rather than cover part of it, which the PDF splitter does.