Is blur enough to hide sensitive text?

People reach for blur because it looks like a privacy tool and because it does not shout. A black bar looks like a redaction, which is awkward in a chat screenshot you wanted to feel casual. That awkwardness is useful. It tells the reader the cover was deliberate. A gentle blur tells them the area is still a picture of text, and their eyes do the rest.

The editor on this site applies the blur inside the rectangle you draw and exports a PNG of the result. It does not keep a reversible layer, and it does not upload the image to apply the effect. That still does not make a weak blur safe. Safety here is whether a person looking at the file can recover the meaning, not whether a server stored a copy.

Use a simple test before you argue about algorithms. Look away from the covered line, look back, and try to read it at the size the recipient will see. Then zoom in. If you can tell it is a six-digit code, or that the word is short and starts with a tall letter, it is not done. Raise nothing about the old box. Undo it, increase the strength, and draw again. The strength slider applies to the next box, not to boxes you already placed.

Short secrets are the worst match for blur. A password of eight characters, a six-digit code, and a card’s last four digits are easy to constrain. You already know the alphabet, the length, and often the pattern. A fuzzy image of that pattern is a puzzle, not a destruction of the information. A long paragraph of ordinary prose is harder to reconstruct, and it is also rarely the thing you were worried about.

Contrast matters as much as strength. Black type on a white form survives a light blur as gray bars with familiar gaps. White type on a dark code editor does the same in reverse. The blur mixes neighbors, so a character surrounded by empty background keeps a silhouette. That is why “it looks fuzzy on my phone” is a bad stopping rule. Phones are small. The file is not.

Watch the edges. Italic text, underlines, subscripts, and the tail of a letter y or g escape a box drawn tight to the highlight. So does the caret in a focused input, and the dots of a “show password” field that you thought were already hidden. Cover the whole control, including the icon, if the icon layout reveals that a value is present and how long it is.

Required is a practical word here, not a statute. If the string is a credential, a government identifier, a full payment number, a precise home address, or a private message you do not have permission to publish, paint it black. Do that even if the blur “looks pretty gone.” Pretty and gone are different. The black box replaces the rectangle with solid black in the exported PNG, so there is no letter shape left in that region.

Draw the bar a little larger than the glyphs. Several bars are better than one bar that also covers the button, the error code, or the column header someone needs. On a bug-report screenshot, cover the query string and leave the path. On a form, cover the value and leave the label. On a chat, cover the other people’s names and leave the sentence that explains your question, unless that sentence is the secret.

A black box is not a certification that a court, a hospital, or an employer will accept the file. Those settings often have their own method, their own reviewer, and rules about the original document. Follow that process. Use this editor only as the step that changes pixels in an image. If the source is a PDF, screenshot the page or export an image of it first. This site does not open PDFs.

Pixelate averages the rectangle down to a grid and stretches it back. Inside one block, the original detail is gone, replaced by a flat color. That sounds stronger than blur, and for a face it often is, because you need the person not to be recognizable and you want viewers to see that the cover was intentional. Text is a different problem. A letter that spans many small blocks is still that letter. You do not need a recovery tool. You need to be able to read.

If you do use pixelate on text that is not a secret, make the blocks large and cover the whole line, not a stripe through the middle. A stripe leaves the tops of the letters, which is enough for many words. Then do the same export check you would do for blur. If you can read it, it failed, regardless of which mode felt more technical.

Some editors market pixelate as permanently safe and blur as always reversible. That slogan is too clean. A coarse pixelate does destroy detail inside each block. A fine pixelate can leave text readable. A strong blur also replaces the original pixels in the export, and it can still leave a guessable shape. The decision is the content and the result you can see, not the name of the filter.

The preview while you are drawing is optimistic. You know what the text said, so your eye fills it in, and you are also looking at a scaled-down canvas. The recipient gets the file. Open redacted-image.png, which is the name this editor downloads, and read it the way you would read a screenshot from a stranger. Corners, tab titles, and the smallest row of a table are where leftovers live.

Do not stack a second blur on a weak one and call it stronger. Undo the weak box, move the slider, and draw a new box. Do not crop after export in a way that brings the original back from another file. The original is still on your device, unchanged, because the editor never overwrites it. That is what you want until the moment you attach the wrong one.

If the image is going to a public issue, a social post, or a document that will be copied, assume the file outlives the conversation. A black bar you can explain in one sentence is a better outcome than a blur you have to apologize for. Paste the screenshot into the homepage editor, choose the mode for the next box, and export. The image is not uploaded for that edit.