OneTaskBy Tim King · Updated
Compare Two Videos
Play Two Clips Side by Side in Sync
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How the Compare Two Videos works
Compare two videos by playing them next to each other, started at the same moment and held in step. Select both files together, choose side by side or stacked, and press Play both. Pick which clip you hear. Both videos play in your browser and neither is uploaded.
Some differences only show in motion. Two takes of a performance, an original and a re-encode, a coach's demonstration and a student's attempt, or this year's swing against last year's: seeing them together at the same instant makes the difference obvious in a way that switching between tabs never does.
How compare two videos works
Both clips are loaded as normal browser video players with no re-encoding. Play both starts them together from the first clip's position. Four times a second the tool checks how far apart they are, and if the second clip has drifted more than a tenth of a second, it is pulled back into line with the first.
Drift happens because each player decodes on its own and a busy computer can delay one. Small amounts are corrected without you noticing; a visible jump means the computer is struggling.
Choosing a layout
| Your clips | Best layout |
|---|---|
| Two landscape videos | Stacked, for a bigger picture each |
| Two vertical phone videos | Side by side |
| Quality comparison of one shot | Side by side, then zoom the browser |
| Technique comparison | Side by side at 0.5 or 0.25 |
Sound from
Two soundtracks at once is noise. Choose First or Second to hear one and mute the other, or None to watch in silence. Switching between them while playing is a quick way to compare audio, such as two mixes or two microphones.
Tips and pitfalls
Line the clips up first. If one clip starts earlier, the two will be out of step for the whole comparison. Trim the earlier one with the video trimmer so both begin at the same moment, such as a clap, a whistle or the first frame of a movement.
Different lengths are fine. When the shorter clip ends it stops on its last frame, and the longer one carries on.
Quality comparisons need the same size. Encoding artefacts are easiest to see when both clips show at the same scale. Compare a 4K and a 1080p file and the browser rescales both to fit.
How to read the result
The stats show each file's resolution and length, the current position, and the drift between the two clips. A drift under 0.05 s is effectively in sync.
FAQ
How do I play two videos side by side?
Select both files together in the file picker, holding Ctrl or Cmd, or drop both onto the page. Choose Side by side and press Play both. The second video follows the first and is kept in sync until you pause.
Can I compare videos in slow motion?
Yes. Set Speed to 0.5 or 0.25 before pressing Play both. Both clips slow together and stay in step, which suits comparing sports technique, dance moves or two takes of the same fast action shot.
What if the two videos start at different points?
The tool starts both from the same time, so a clip that begins later stays behind. Trim the start of the earlier clip so both begin on the same event, then load them again. Pause also re-syncs them.
Are my videos uploaded to compare them?
No. Both files are opened and played by your browser on your own device. Nothing is sent anywhere, so you can compare unreleased edits or private training footage safely, and even work offline.
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