How to sync a reaction video with the video you reacted to
Your camera and the video were recorded as two files, and they rarely start at the same instant. Syncing is sliding one against the other until your reaction lands on the moment that caused it. Here is how to tell whether you need to, and the quickest way to do it.
1 s, 0.1 s or 1 framethe steps you move the video by
Loop 5sthe same moment, again and again
Same length?then there is nothing to line up
First, check
You may not need to sync at all
The lengths of the two files tell you which case you are in, and the editor reads them the moment both are added.
Same length
One session caught both
A recorder that saved your camera and the screen as two files at the same time gives two files that start at the same instant. Step 2 says there is nothing to line up, and you can go straight on. Press Play once if you want to be sure.
Different lengths
Two recordings, two start times
A phone on a tripod and a downloaded episode, or a webcam and a trailer, were started by hand at different moments. Then the video has to be moved until both run together, and the rest of this page is for you.
Getting close
Three ways to find the spot
Your camera sits on the top track and never moves. The video is the track below it: drag it left or right, or type the exact seconds if you already know them.
1
Listen for the echoIf your microphone picked up the video’s sound, every noise plays twice while the two are apart. Drag the video until the two sounds merge into one. That position is the right one, and it is usually the fastest of the three.
2
Use a moment you cannot mistakeOn headphones there is no echo. Pick a jump scare, a punchline or a goal, put the playhead on your reaction, and move the video until its cause shows up at the same instant.
3
Leave yourself a marker next timeStart recording first, then start the video and clap or snap on its very first frame. The clap is easy to find on your waveform, and the start of the video goes right on it.
Getting it exact
Fine tuning, without starting over
Everything below sits next to the picture in step 2.
Loop 5s
Repeats the five seconds under the playhead, so the sound never stops while you adjust.
Nudge by 1 s, 0.1 s or a frame
Minus moves the video earlier, plus moves it later. Get close with seconds, finish with frames.
Balance what you hear
Turn one side down, or hear the camera only or the video only. It changes this screen, not the finished mix.
Trim the video’s ends
Drag the edges of the video track to drop a logo at the start or credits at the end.
Keyboard
Shortcuts in step 2
The same list is behind the keyboard button on the step itself.
Getting around
SpacePlay or pause both
←→Playhead one second
Shift←→Playhead a tenth of a second
HomeEndThe start or the end
Moving the video
[]The video one frame
Shift[]A tenth of a second
0Back to zero, both start together
LLoop the five seconds you are on
Before you press record
Make the next sync easier
Record both at once
If your recorder can save the camera and the screen as two files at the same time, they come out already in sync.
Clap on the first frame
One sharp sound at the start is worth ten minutes of searching for the right moment later.
Headphones or speakers, on purpose
Speakers make the echo method easy, headphones keep your voice clean. Choose before, not after.
Pause both or neither
The sync is one position for the whole recording. Pausing only the video makes everything after it drift.
Questions
What people ask about syncing
Does ReactionCut sync the two recordings automatically?
Not by listening for you. If both recordings are the same length, they come from one recording session and already start together, and step 2 tells you so. Otherwise you line them up by hand with the echo, a marker or one unmistakable moment.
How precise does it need to be?
Close enough that your laugh lands on the joke. Get near with the one-second and tenth-of-a-second steps, then finish with the one-frame buttons while Loop 5s repeats the moment. A frame, a 25th of a second, is the smallest step there is.
I paused the video while I kept recording. Can it still line up?
Only one part of it. The sync is one position for the whole recording, so everything after the pause drifts by however long the pause was. Next time, if you need a break, stop your recording and the video together, or neither.
Should my microphone pick up the video’s sound?
On speakers it will, and that makes syncing easy, because you can hear the echo disappear. The bleed stays in your voice track, though. Headphones give a cleaner voice; then use a marker or a moment you cannot mistake.
Is the sync saved if I close the tab?
No. It belongs to those two recordings, and they are only open in that tab. Your looks stay in the browser. The sync starts over at zero when you add the files again.
Why does the sync matter for the cuts?
The automatic cuts in step 5 are measured from it. The editor listens to your camera to find where you talk, and the sync decides which moment of the video that talk belongs to.
Line up your two recordings
Free in your browser. Your files stay on your computer while you do it.