Bug reports die when the only readable part of the PNG is fog. Someone ran a full-frame filter because the editor offered a slider, then the recipient cannot see the broken button, the quiz prompt, or the status code that justified the capture. A useful screenshot is evidence with one dead region, not a discarded photo with extra steps.
This page owns partial cover only. You pick a region with Box or Draw, add padding so a descender or digit gap cannot peek out, zoom to full size to verify, and leave everything else sharp on purpose. The full stills workflow (tool choice, optional detection, PNG habit) lives on how to blur a screenshot. Here the skill is the tight region.
How to blur only part of a screenshot
One tight region per secret beats one giant fog. Add padding past the ink. Zoom until you would bet on a leftover glyph, then enlarge the cover if you would.
In BlurThis
These steps are only about placing and verifying a partial cover. Open the screenshot blur tool, then:
- Choose Box for rectangular UI (toasts, list rows, title bars). Choose Draw when the secret is not a clean rectangle.
- Press at one corner of the secret (or start a closed outline for Draw), drag with padding past descenders and digit gaps, then release.
- Apply Black bar for phones, emails, OTPs, and keys. Apply Blur or Pixelate for faces when glance-level cover is enough.
- Zoom until one character is large. If you can name it, undo and enlarge the region. Repeat for each secret as its own box.
- Tap Download PNG, open the export at full size, then send that file.
Open larger image in a new tabWhy partial cover beats full-frame blur
Full-frame blur feels private and often wastes the capture. A manager cannot see the broken control. A teacher cannot see the question. A friend cannot see why the chat was funny. Light full-frame blur still leaks layout, app chrome, and sometimes readable headings. Heavy full-frame blur is a discarded screenshot with extra steps.
Locate the secret. Cover that region. Keep the error message, the button, the timestamp, and the surrounding UI readable. On BlurThis, the Box gesture is press, drag, release. Draw is trace a closed loop, release, then fill. People who search “blur part of image online” usually want that boxed region, not a whole-picture filter. The same idea applies to any photo, not only screenshots.
Box, Draw, padding, and zoom
Box is the everyday tool for UI. Press at one corner of the secret, drag to the opposite corner, release. Include padding: a letter that sticks out of the cover is a clue. Descenders on g, y, and j, and the spaces in a phone number, are the usual leaks. A box that kisses the ink looks tidy in a thumbnail and fails at full size.
Draw helps when the secret is not a rectangle: a tilted badge, a signature flourish, hair around a face. Draw traces a closed outline, then fills or blurs that enclosed region evenly. It is not a paintbrush that smears while you drag. You finish the loop, then the fill lands. A smear brush leaves thin spots where your finger sped up. A closed selection fills once at the strength you set. Overlapping boxes are often enough for irregular UI; overlap is cheaper than a leak.
Padding is the difference between a bar that looks finished and a bar that fails under zoom. Leave a margin past the character boxes, past the formatted spaces in a phone number, and past any underline or selection highlight that still sketches the string. If the cover ends on the ink edge, widen it.
Zoom is how you verify. Composer previews shrink the problem. Use the plus control or a pinch until one character is large. If you can name it, enlarge the region and export again. Optionally tap Find faces or Find text for suggestions, then still walk the chrome by eye. Suggestions miss quoted replies and faint chips.
Open larger image in a new tabSeveral secrets in one shot
Do not grow one giant fog over the middle. Make separate tight covers: chat name, phone, quoted reply. Readers can still see the bug you are reporting. Inbox list views need a bar per row you cannot crop. Gmail is famous for this: you meant one thread, and the list still prints five other subjects.
Sidebars are their own region. Slack workspaces, Teams org names, Discord servers. If the sidebar is not part of the story, crop it at capture time. If you already captured, bar the strip. Do not soft-blur a column of emails. Face blur or pixelation on one tile does not make a person unidentifiable if the display name, a jersey, or the next screenshot still points to them. Cover those copies as their own regions.
Editing stays in the browser tab on BlurThis. Your file is not sent to BlurThis servers for processing. Prefer Download PNG so you inspect a flat cover before you attach it. After pixels are fully replaced and flattened, later JPEG compression cannot put the originals back. A weak smear or a gap still can leak.
When crop is enough instead of a box
If the secret lives only in a corner, cut the photo. Menu bars, taskbars, keyboards, notification banners. Crop cannot save you if the email sits between two paragraphs you must keep. That is what a bar is for. Crop versus bar is the longer fork. People crop too tight and clip the error code they needed. People crop too loose and keep the account switcher. Check once at the actual pixel size, not in a tiny composer preview.
Treat phones and emails as opaque bars, or crop them. Cover the digits, the country code, the formatted spaces, and the repeats in headers and quotes. Partial cover fails when you bar the bubble and leave the header. Details: hide a phone number or email.
Watermarks, Undo, and a tight-box checklist
Watermarks and stamps that sit on top of an image in another app can be layers. Flatten. A box you drew in a slide deck might still be an object someone can move. A downloaded PNG from a canvas is pixels. Send that file. Undo exists so you can tighten a box. A first drag that clips a digit is worse than a second drag that looks slightly ugly. Ugly bars are honest. Pretty short bars leak.
- One region per secret, with padding.
- Headers and quotes get their own boxes.
- Zoom in. If you can guess a character, enlarge the cover.
- Export PNG, open it at full size, then send the export, not a photo of the editor.
Troubleshooting
- The whole image went soft. You used a full-frame filter. Undo. Drag a box on the secret only.
- The error is unreadable too. Your box was too big. Undo and drag tighter, or crop the chrome first.
- A letter peeks out. Add padding. Descenders and the gaps between digit groups are the usual leaks.
- Draw left a patchy scribble. You treated it like a brush. Undo, zoom in, and trace one closed loop with padding. The face-and-signature walkthrough is blur an image with Draw.
- You screenshotted the editor to save. Download instead. A snip of the browser adds chrome and another compression pass.
Recap
Partial redaction looks like more work than a full-image filter. It is less work than explaining a leak, and it leaves the screenshot useful. Mark the region. Stop there. Bar numbers. Keep the rest sharp. Draw closes a shape, then fills it. Zoom until you would bet on the leftover glyph, then enlarge the cover if you would.
Explore the wider map in the how to blur hub. For local processing habits, see blur a screenshot online without uploading. Device Markup and Paint steps: iPhone, Android, Windows, Mac.
