Guide
Blur, pixelate, or black box: when each is appropriate
The three modes in the editor are not styles for their own sake. They destroy the original pixels in different ways. Pick the one that matches how badly the hidden part must stay hidden, and how much of the picture still has to make sense.
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What does blur, pixelate, and black box each do?
Blur mixes pixels inside the box you draw, pixelate replaces that box with large flat blocks, and black box paints it solid black. The rest of the image stays sharp. Blur and pixelate can leave shapes you can still guess. Black box removes the picture in that rectangle from the exported PNG.
Blur runs a blur filter over the rectangle you draw. Nearby pixels mix. At a low strength you can still see that a line of text was text, and sometimes you can still guess a short word from the shape. Raise the strength until the region is a smear. The rest of the image stays sharp because the filter is clipped to the box.
Pixelate shrinks that rectangle to a coarse grid and stretches it back. You get blocks of flat color. Large blocks hide more. Small blocks look neat and hide less, especially on big type. People recognize pixelate as “this was hidden on purpose,” which is useful in a photo where a soft blur would look like a camera mistake.
Black Box replaces the rectangle with solid black. The original colors are gone from the exported PNG. There is no letter shape left to squint at. It looks like a document redaction because that is what it is. It is also the least subtle, so it is a poor choice when you only want a background face to recede and a good choice when the alternative is leaking an account number.
When is blur the right cover?
Use blur when the scene should still look like a photo and the hidden detail is not a secret. A background face or a screen with no large type can take a strong blur. Passwords, keys, card numbers, and ID numbers should not. If you can still read it, raise the strength and draw again.
Blur fits a background face in a street photo, a bystander in a group shot, or a screen in the background of a desk photo when the screen is not showing secrets in large type. You want the viewer to understand the scene and not to read the detail. Turn the strength up and then look away and look back. If you can still read it, it is not done.
Blur is a weak choice for passwords, API keys, recovery codes, card numbers, and government id numbers. Those strings are short, high contrast, and worth guessing. A frosted look feels polite and fails the actual job. If you are unsure, do not use blur.
The slider applies to the next box you draw, not retroactively to boxes you already placed. If the first box is too weak, undo it and draw again after you raise the strength. Stacking a second blur on the same spot is an unreliable way to “make it stronger.”
When should you pixelate instead?
Pixelate when you want the cover to look intentional, as in a news photo of a face or a license plate. Large blocks hide more. Small blocks look tidy and can leave an eye or a letter intact. If the text is a secret rather than a face, do not rely on a mosaic. Switch to a black box.
Pixelate is the familiar mosaic from news photos and video. It tells the viewer that a face or a plate was covered, which blur sometimes fails to do if the blur is gentle. Use it for faces in photos you are publishing, for license plates when you want the car to remain recognizable, and for chat avatars when a black rectangle would wreck the layout you are trying to show.
Make the blocks large enough that an eye, a letter, or a digit does not survive inside one block. On a face, include the hairline and ears if the person would still be recognizable from those. On a plate, cover the whole plate, not only the characters. A regional sticker or a frame slogan can identify a car almost as well as the number.
Pixelate is still a visual disguise, not a cryptographic one. Very small blocks over very large text can leave a readable rhythm. If the text is a secret rather than a face, switch to black.
When is a black box required?
A black box is required when a stranger could use the text: passwords, tokens, national ID numbers, full card numbers, and precise addresses you do not need to show. Draw the bar a little larger than the letters. Several small bars are better than one bar that also hides the thing you are trying to explain.
Black box is the default for anything you would not read aloud in a public ticket: passwords, tokens, national id numbers, full card numbers, medical record numbers, and precise home addresses when the rest of the image does not need them. Draw the box a little larger than the glyphs. Italic text and underlines escape tight boxes.
Several small boxes are better than one box that also hides the bug, the form label, or the button you are asking someone to look at. A page of black bars is honest. A page that is one black rectangle is useless. Leave the labels of form fields if the labels are generic (“Email”) and cover the values.
Black box does not grant a legal redaction by itself. Courts, hospitals, and some employers have their own rules about how a document must be redacted and who must approve it. This editor replaces pixels in an image you export. It does not certify that you met a policy. If you are redacting for a filing, follow that filing’s rules and use this only as the pixel step.
Which mode should you pick in a hurry?
If reading the hidden part could harm someone, use a black box. If the goal is only that a person or a plate is not recognizable at a glance, pixelate or a strong blur is usually enough. If you are unsure, use black. Export, open the PNG at full size, and try to read every region you touched.
If a stranger could harm someone by reading the hidden part, use black box. If they only need to not recognize a person or a plate at a glance, pixelate or a strong blur is usually enough, and pixelate is the clearer signal. If you would be embarrassed but not endangered, blur is fine once you have checked that you cannot read it.
After you export, open the PNG at 100 percent and try to read every region you touched. The original file is still on your device. Share the PNG, not the original. The homepage editor starts on blur; the black-out page starts on black box. They are the same editor. The mode is a choice you can change before the next box.
- Secrets, tokens, passwords, id numbers: black box, with padding.
- Faces and plates you are publishing: pixelate, large blocks, whole region.
- Background clutter you want to soften: blur, strength high enough that text is gone.
- Anything you are unsure about: black box. You can explain the bar in a caption. You cannot unsend a leaked key.
Questions about this
These are the decisions people stall on: whether a blur can be undone, whether pixelate is safer than blur for a password, and whether a black box is a legal redaction. The short version is visual. Check the export with your eyes. This editor does not certify a filing.
Can someone turn off the blur in the downloaded PNG?
No. The export is a new image with the filter already applied, not a layer you can switch off. A weak blur can still be guessed by eye, which is why secrets belong under a black box. The original file on your device is unchanged, so do not share that file.
Is pixelate safer than blur for a password?
Not if the blocks are small and the type is large. The letters can remain readable without any special software. Use a black box for passwords, keys, and ID numbers. Use pixelate for faces and plates when you want the hiding to look intentional.
Does a black box meet a legal redaction standard?
Not by itself. Courts, hospitals, and some employers specify how a document must be redacted. This tool replaces pixels in an image you export. Follow the rule that applies to your filing, and use the editor only for that pixel step.
Where should you go next?
Apply the cover in the same local editor this guide describes. Paste a screenshot on the homepage, or open a related note if the leak is a different kind. These links are the next step. They are not separate tools that upload the file.