My crop looks shifted or padded with black. What went wrong?

Your rectangle probably exceeded the source frame on at least one edge. Recompute X plus width against the source width and Y plus height against the source height, then retype whole-pixel values that fit inside. Invalid rectangles fail without shifting, clipping, rounding, or producing a partial file, so retype the coordinates before running the crop again.

The WebM has no sound even though the source did. How do I fix it?

Audio is appended only when the browser exposes a capturable track through media capture. Try a different browser, re-encode the source to a codec the browser captures audio from, or accept a silent output and add audio separately. The crop itself cannot recover audio the browser never saw.

Why does the destination player show no duration on my cropped WebM?

The recording pass streams MediaRecorder output, which often omits a finite container duration. The tool then patches a big-endian Matroska Duration in timestamp-scale ticks. If the player still reports zero or live, the file is fine but that player is reading the WebM before the patched value; open it in a standards-compliant player to confirm.

Can I just nudge X and Y by a few pixels and re-crop to fix it?

Yes, as long as the new X plus width and Y plus height still fit inside the source frame and the output area stays at or below 3840 by 2160 pixels. Nudging is the standard way to correct an off-by-one, and because processing is real time you can iterate quickly on short sources.

Does the crop preserve subtitles, HDR, or rotation?

No. The crop re-records a single fixed rectangular region into a Canvas and saves it as WebM. Subtitles, chapters, attachments, rotation tags, HDR signaling, and color metadata are not preserved, so review the output rather than assuming the file behaves like the source.

Fix a Cropped Video Result That Looks Wrong

Cropping a video locally produces a wrong-looking result when the rectangle you typed does not match the area you wanted, when it slips past the edges of the source frame, or when the browser silently drops audio, duration, subtitles, or rotation metadata during the re-recording pass. The fix is almost always the same: re-open the source in the Video Cropper, confirm the decoded dimensions, retype X, Y, width, and height as whole nonnegative pixels that stay inside every frame, run Crop video again while keeping the tab open, and fully review the new WebM before you delete the original.

The search query itself tells you the reader has already attempted a crop and is unhappy with the output, so this article treats the "fix" as a deliberate re-run with corrected coordinates rather than as a first-time walkthrough. The Video Cropper records a fixed rectangular region of the source into a Canvas and saves that stream as WebM; if the result looks wrong, the rectangle, the source, or the browser encoder is the culprit, and the remedies below target each of those in turn.

how do i fix a result that looks wrong after i use video crop — Fix a Cropped Video Result That Looks Wrong

What "Looks Wrong" Usually Means

Wrong-looking crops cluster into a handful of recognizable failure patterns, and recognizing which one you have narrows the fix.

Wrong area shown. The WebM opens but shows a slice you did not intend, such as the top-left corner instead of the centered subject. This points to X and Y values that are too small, or to width and height that strayed from the in-frame region you measured.
Black bars or shifted frame. The output looks offset, padded, or boxed by darkness. This usually means the rectangle exceeded the source frame on at least one edge, so the request was rejected because X+width or Y+height left the decoded bounds.
No sound. The WebM plays but is silent. The browser did not expose a capturable audio track through media capture for this particular source, so no audio was appended to the Canvas stream.
Wrong duration. The output plays only a few seconds, or the destination player reports a missing or zero duration. Streaming MediaRecorder output can omit a finite container duration, so the player falls back to live mode.
Muddy, blocky, or oversize picture. The crop looks soft, pixelated, or much larger than you expected. The encoder derived a bitrate from the cropped area, and fast motion, source grain, or codec choice changed the on-disk size.

Fixing the Crop with Exact Pixel Coordinates

Run through these steps in order. They are the official operating sequence for the tool, and following them removes the variables that most often produce a wrong-looking result.

Choose a browser-decodable video (MP4, WebM, MOV, M4V, or Ogg) from your local drive and wait for the decoded source dimensions to appear in the tool. Do not type coordinates before these load, because every later check depends on them.
Read the reported width and height, then plan a rectangle in whole pixels that sits entirely inside them. The defaults already select the full frame, so use those numbers as your upper bound.
Enter X and Y as pixel offsets from the source frame's top-left corner. X moves the crop right; Y moves it down. Enter width and height as the horizontal and vertical extent of the crop. Every value must be an untrimmed nonnegative whole pixel count, and width and height must each be at least two pixels.
Verify two boundary checks: X + width must not exceed the source width, and Y + height must not exceed the source height. Multiply width by height and confirm the result is at or below 3840 × 2160 pixels (8,294,400). If either check fails, the rectangle is rejected without shifting, clipping, rounding, or producing a partial file.
Select Crop video and leave the tab open. The tool plays the source locally, draws only the requested region into an equal-size opaque Canvas at 30 fps, and records that Canvas stream as WebM. A one-minute source takes about one minute to finish.
When the download appears, save the WebM, then play it from start to finish in the destination player. Check the picture, the audio, and the duration before deleting anything.

For example, suppose the source decodes to 1920 × 1080 and you want a centered 1280 × 720 window offset 320 pixels right and 180 pixels down. Type X = 320, Y = 180, width = 1280, height = 720. The boundary sums are X + width = 1600 (less than 1920, valid) and Y + height = 900 (less than 1080, valid). Output area is 1280 × 720 = 921,600 pixels, well under the 3840 × 2160 cap. That single calculation is the kind of check worth doing by hand before you click Crop video; if any of the three numbers break, the request is rejected and nothing is produced.

Limits That Cause a Failed or Wrong-Looking Crop

The Video Cropper enforces a small set of numeric limits. Every one of them can independently turn a "fix" into another wrong result, so keep them visible while you retype coordinates.

Parameter	Required value	Why it matters
X offset	Nonnegative whole pixel	Moving the crop left of frame zero places part of the rectangle outside the source.
Y offset	Nonnegative whole pixel	Same idea for the vertical axis.
Width	At least 2 pixels	Widths below 2 pixels are rejected.
Height	At least 2 pixels	Same idea on the vertical axis.
X + width	≤ source width	Past the right edge, the rectangle is invalid and rejected.
Y + height	≤ source height	Past the bottom edge, the rectangle is invalid and rejected.
Output area	≤ 3840 × 2160 pixels	Beyond this, the Canvas is rejected even if the source is larger.
Source side	≤ 4096 pixels	Taller or wider sources are blocked at the shared video safety budget.
Source duration	> 0 and ≤ 5 minutes	Zero-duration or longer sources are rejected up front.
Source file size	≤ 500 MiB	Larger files fail the explicit positive-file budget.

If your fix attempt fails silently, walk back through this table before assuming the tool is at fault. Most wrong-looking crops are not encoder bugs; they are a single off-by-one coordinate or a forgotten boundary check.

Audio, Duration, and What Doesn't Survive the Crop

A crop can look perfect and still feel wrong because audio or duration behavior surprised you. Knowing in advance which properties the tool preserves makes the "fix" faster.

Audio is appended to the Canvas stream only when the browser exposes a capturable audio track through media capture from DOM elements. Support varies by browser and by source codec, and the source may play audibly during the real-time processing pass. If your output is silent, the source itself may not have exposed a track, not the crop. Test with a short sample first if audio matters.

Duration is patched after recording. The tool uses the standards-tested WebM duration writer shared with Video Compressor: it parses Segment Info and TimestampScale and inserts a big-endian Matroska Duration value in timestamp-scale ticks, following the Matroska container format. The result must remain nonempty and decode with the requested dimensions; if either check fails, the recorded Blob is discarded. If your destination player still shows a zero or missing duration, the file is fine but the player is reading the WebM before the patched duration; open it in a standards-compliant player to confirm.

What the crop deliberately does not preserve: subtitles, chapters, attachments, rotation tags, HDR signaling, color metadata, and many other container features. It also does not preserve every property of the input. It changes the visible frame region, and it is not a trim-by-time, resize, compress-only, redact, blur, or object-removal tool. Treat each output as a new file whose compatibility you confirm, rather than as a property-preserving edit of the source.

Verifying the Fixed Crop Before You Delete the Source

A fix is not finished when the WebM downloads. The product contract is explicit: keep the original until the entire output has been reviewed. Run this short verification pass each time.

Play the WebM from the first frame to the last and confirm the rectangle matches your intent in every scene, not just the first frame. One fixed rectangle is applied to every frame, so a scene that pans can reveal an off-by-one you missed at the start.
Confirm duration. If your player reports a finite duration in seconds, the Matroska Duration patch took; if it reports live or zero, the player is reading the stream before the patch and you may need a different player.
Confirm audio. Listen for the full length; remember the source may have been audible during processing and the output silent if the browser did not expose a track.
Confirm compatibility by importing the WebM into the destination player, editor, or platform you actually plan to use. A file that opens in your browser is not guaranteed to open everywhere.
Only when all four checks pass, delete the source.

If the output still looks wrong after this pass, the most productive next step is to review a pre-crop checklist so the next fix attempt lands on the first try; the Avoid Mistakes When You Crop a Video guide covers the same coordinate math in checklist form and pairs naturally with the limits table above.