How to blur sensitive screen content in a screen recording
- Step 1Drop in the screen recording — MP4, MOV, MKV, WEBM and AVI are all accepted. Screen-capture tools often output MP4 or WEBM; both load locally via FFmpeg.wasm. One file at a time.
- Step 2Jump to where the secret appears — Set Start (s) to the moment the sensitive panel shows up — the picker renders that exact frame, so you can frame the box over the real content (the terminal, the CRM row, the chat thread).
- Step 3Draw the box over the panel — Screen content is rectangular, so dragging a box over a window or sidebar is exact. Use click-drag-inside to reposition and the SE corner to resize until it covers the full panel including any line that might scroll into view.
- Step 4Set the time window — Enter End (s) for when the secret is no longer visible. If the key is on screen the whole time, leave End at its default (end of clip). The region outside the window stays unblurred.
- Step 5Set a strong blur — Text is the hardest thing to obscure, so use a high Blur strength. Because the radius caps at half the smaller side of the box, a generously sized panel box blurs harder than a thin strip over a single line — prefer covering the whole panel.
- Step 6Export and read-test the result — Process to MP4, then try to read the secret in the output at full screen, frame by frame across the window. If any character is legible, enlarge the box or raise the strength and re-export before sharing.
Screen-content redaction patterns
Common sensitive panels in screen recordings and how to box them.
| What's exposed | Box it over | Strength / window tip |
|---|---|---|
| API key / token in a terminal | The whole terminal output area, not one line | High strength; bigger box raises the radius cap |
| Password field on a login form | The field plus any autofill dropdown | Cover the full field height |
| Customer PII in a CRM row | The row(s) containing the data | Window to the seconds the row is visible |
| Private chat / Slack thread | The message pane sidebar | Whole-clip window if it stays open |
.env file scrolling past | The editor pane while it's visible | Short, precise time window |
What the redactor does to a screen recording
Fixed processing behaviour you can rely on.
| Property | Value |
|---|---|
| Processing | In-browser FFmpeg.wasm — no upload |
| Region | One rectangle per pass; boxblur over crop |
| Output | MP4 / H.264 (CRF 20, preset medium) |
| Audio (voiceover) | Stream-copied, unchanged |
| Blur radius | strength (5–50), capped at min(W,H)/2 |
| Max file (Free / Pro / Media / Dev) | 1 GB / 10 GB / 100 GB / 100 GB |
Cookbook
Recipes for the recordings developers and support teams actually need to redact.
Blur an API key that flashes in a terminal for 3 seconds
A live key prints in your terminal between 0:22 and 0:25 during a deploy demo. Box the terminal output area and window it tightly.
Source: deploy_demo.mp4, 2560x1440 Redact rectangle: X=120 Y=820 Width=1200 Height=260 Start (s): 22 End (s): 25 Blur strength: 50 radius = min(50, floor(260/2)) = 50 (full strength) Filter: [0:v]split[base][redact];[redact]crop=1200:260:120:820,boxblur=50:1[blur]; [base][blur]overlay=120:820:enable='between(t,22.000,25.000)'[outv]
Hide a Slack thread for the whole tutorial
A private channel stays open in the left sidebar the entire recording. Box the sidebar and leave the window at default so it's blurred start to finish.
Source: feature_walkthrough.webm, 1920x1080 Redact rectangle: X=0 Y=120 Width=300 Height=900 Start (s): 0 End (s): (whole clip) Blur strength: 35 Output: feature_walkthrough.mp4 (voiceover preserved via -c:a copy)
Redact two panels (run twice)
Both a terminal and a browser address bar show secrets. Blur one per pass: terminal first, then feed the MP4 back for the address bar.
Pass 1: rec.webm -> terminal box -> step1.mp4 Pass 2: step1.mp4 -> address-bar box (X=400 Y=60 W=900 H=40) -> final.mp4
Thin one-line box doesn't blur enough — widen it
A 700×24 strip over a single key line barely blurs because the radius caps at 12. Box the whole terminal pane instead.
Strip: 700x24, strength 50 -> radius = floor(24/2) = 12 (text still legible) Pane: 700x300, strength 50 -> radius = floor(300/2)=150 -> clamped to 50 Result: full strength once the box is tall enough.
Mute a spoken secret alongside the visual blur
You read an access token aloud while it was on screen. Blur the panel here, then mute that span with audio-mute-region so the secret isn't in the soundtrack.
Step 1: rec.mp4 -> redact terminal box (22s-25s) -> visual_done.mp4 Step 2: visual_done.mp4 -> audio-mute-region (22s-25s) -> safe.mp4 Visual + audio secret both removed.
Edge cases and what actually happens
The secret scrolls and the box misses a line
By designThe box is static. If the terminal scrolls and a key prints just above or below your box, it stays visible. Box the entire pane height, not a single line, or split into time-windowed passes for each scroll position.
Single-line strip blurs too weakly
Insufficient radiusA short box has its boxblur radius capped at half its smaller side, so a 24-pixel-tall strip can only blur a little. Box the whole panel so the height raises the cap and the text is properly scrambled.
Spoken secret left in the audio
PreservedAudio is stream-copied. If you narrated the password or token aloud, the visual blur won't help — mute that exact span with audio-mute-region.
Secret appears more than once in the recording
PreservedEach pass blurs one rectangle for one window. If the key reappears in a second panel or a second moment, run the output through the tool again with the appropriate box and window.
Output is MP4 from a WEBM screen capture
By designScreen captures often record WEBM (VP8/VP9); the redactor always outputs H.264 MP4. If you need WEBM back for the web, transcode the result with the video-transcoder.
Whole recording recompressed
ExpectedThe full video stream is re-encoded at CRF 20 because the filter graph touches it. Text-heavy screen content at CRF 20 stays sharp, but if you want to recompress as little as possible, trim to the relevant segment first with the lossless-trimmer.
Recording embeds window title / app metadata
PreservedPixel blur doesn't strip container metadata. If your capture tool wrote identifying tags, run the redacted file through the metadata-scrubber before publishing.
Long 4K recording exceeds Free tier
Tier limitA long high-resolution screen capture can pass 1 GB (the Free cap). Upgrade for more headroom (Pro 10 GB, Pro + Media / Developer 100 GB) or trim to just the section you're publishing first.
Frequently asked questions
Is it safe to redact a recording with live credentials in it?
Yes — that's the point. The file is processed in your browser via FFmpeg.wasm and never uploaded, so the live key or password in the recording is never transmitted to any server. (As a separate precaution, you should still rotate any credential that was on screen.)
Could a viewer recover the blurred text?
No. The boxblur destroys the pixels in the region; there is no hidden layer underneath. Only the area you boxed is affected, so make sure the box covers every line the secret could appear on.
Why does my thin box over one line barely blur?
The blur radius is capped at half the smaller side of the box. A 24-pixel-tall strip can only blur a tiny amount. Box the whole terminal or panel so the height is large, and the text scrambles properly.
I read the secret out loud — does blurring fix that?
No, audio is stream-copied untouched. Mute that span with audio-mute-region to remove the spoken secret from the soundtrack.
Can I blur the panel only while it's visible?
Yes. Set Start (s) and End (s) to the seconds the panel is on screen; the blur is gated to that window and the rest of the demo is unblurred.
My capture is a WEBM — will it work?
Yes. WEBM, MP4, MOV, MKV and AVI are all accepted. The output is always H.264 MP4; transcode back to WEBM with the video-transcoder if you need it for web embedding.
Two different panels show secrets — can I blur both?
One rectangle per pass. Blur the first panel, then run the resulting MP4 back through the tool for the second.
Will the recording lose quality?
The video is re-encoded once at CRF 20, which keeps screen text crisp. To recompress as little as possible, trim to the part you're publishing with the lossless-trimmer first.
Does it remove metadata the capture tool added?
No — blurring is a pixel operation and doesn't touch container metadata. Run the output through the metadata-scrubber if that matters.
Does it detect secrets automatically?
No. You draw the box and set the window manually, which is the reliable approach for arbitrary on-screen text that no detector would recognise. Automatic detection in JAD's video tools is limited to faces (face-blur).
How big a recording can I process?
Free allows 1 GB per file, Pro 10 GB, and Pro + Media / Developer 100 GB, with no limit on length. Long 4K screen captures are most likely to hit the Free cap.
What exactly comes out?
An H.264 MP4 (CRF 20, preset medium) with the audio copied verbatim, with your chosen rectangle blurred over the chosen time window.
Privacy first
Every JAD Video tool runs entirely in your browser via WebCodecs and FFmpeg (WebAssembly). Your video files never leave your device — verified by zero outbound network requests during processing.