Subtitles go out of sync for one of three reasons: the whole file is early or late by the same amount, the file was timed for a different frame rate so the gap grows over time, or the video was cut after the subtitles were made. A fixed delay needs a single time shift. Growing drift needs a frame-rate change or a two-point sync. A cut needs only the part after the cut moved. Find which one you have first, and the fix takes a few minutes.
Player settings such as VLC's subtitle delay only hide the problem while you watch. To fix the SRT file for good, change the timestamps in the file and save a new copy.
Find out which sync problem you have
Play the video with the subtitles on and check three moments: a line near the start, one in the middle, and one near the end. Note how far off each one is, in seconds.
| What you see | Likely cause | Fix |
|---|---|---|
| Every line is off by the same amount | Fixed offset, often from an intro, logo or different release | Shift all cues |
| Fine at the start, worse and worse later | Frame-rate mismatch, such as 23.976 vs 25 fps | Convert the frame rate |
| Off at the start and end by different amounts, not a common frame rate | Different edit speed or encoding | Two-point sync |
| Fine until one point, then off by a fixed amount | A scene, ad break or intro was cut or added | Shift only the cues after that point |
Write the three numbers down. They decide everything that follows.
Fix a constant delay by shifting every cue
This is the most common case, and the easiest. Measure the offset, then add or subtract it from every timestamp.
- Find a clear line of dialogue near the start of the video. Note the time the speaker starts the line, for example 00:01:12.500.
- Open the SRT in a text editor and find that cue. Note its start time, for example 00:01:10,000.
- Subtract: 72.5 minus 70.0 is 2.5 seconds. The subtitles are 2.5 seconds early, so they need to move 2.5 seconds later.
- Open the free subtitle sync tool, drop in the file and enter the offset in seconds. Positive values show subtitles later. Negative values show them earlier. Enter 2.5 for this example.
- Download the new file and test it at the three moments you checked before.
The tool runs in your browser and the file is not uploaded. It accepts SRT, VTT, ASS, SBV, SUB, TTML, SAMI, LRC and CSV files up to 5 MB. VTT and ASS files keep their format; the other formats come back as SRT. If a shift pushes a cue before 0:00, the tool starts it at zero, and a cue that would end before zero is removed. Check the first few lines if your offset is large and negative.
In Subtitle Edit, the same fix is under Synchronization, then Adjust all times (show earlier/later). You can apply it to all lines or only the selected ones.
Test the delay in VLC before you change the file
VLC is a quick way to find the right offset without guessing. While the video plays, press H to delay the subtitles and G to show them sooner (these are the default hotkeys on Windows and Linux). VLC shows the current subtitle delay on screen each time you press a key. You can also set an exact value in Tools, then Track Synchronization.
When the lines match the speech, note the delay value and enter that number in a sync tool or Subtitle Edit. VLC's delay applies only to playback in that player. It does not save the change into the SRT file, so the same subtitles will be out of sync again on a TV, in Plex or on another device.
Fix subtitles that drift: change the frame rate
If the subtitles match at the start but drift further out of sync over time, the file was probably timed against a version of the video that runs at a different speed. The classic case is a film released at 23.976 frames per second and a European TV or DVD version at 25 fps. The 25 fps version runs about 4% faster, so a line that sits at 60:00 in one version appears near 57:32 in the other. That is about two and a half minutes of drift by the end of an hour.
The same problem in a smaller form shows up between 29.97 and 30 fps. That gap is 0.1%, which adds up to about 3.6 seconds per hour: easy to miss in the first scene and obvious by the end.
To fix it:
- Check the frame rate of your video. VLC shows it under Tools, then Codec Information. Many media players and file info tools show it too.
- In the subtitle sync tool, set the original and target frame rates. Common pairs are 23.976 and 25, 24 and 25, or 29.97 and 30.
- Test the end of the video. If the drift got worse instead of better, swap the two values and run it again.
After a frame-rate change, the start can still be off by a fixed amount. Run a normal shift on the result if it is.
Fix drift that is not a frame-rate problem: two-point sync
Sometimes the drift does not match any standard frame-rate pair. For this, use two reference points: one line near the start and one near the end. The tool then stretches or squeezes every timestamp in between so both points line up.
Here is the math, so you can check what a tool is doing. Say cue A starts at 00:02:00 in the file but is spoken at 00:02:03. Cue B starts at 01:30:00 in the file but is spoken at 01:31:00. The file spans 88 minutes between those cues and the video spans 88 minutes 57 seconds. Every timestamp gets stretched by that ratio, measured from cue A, and then moved by the 3-second difference at cue A.
In Subtitle Edit this is Synchronization, then Point sync. Pick a cue near the start, set its correct time, pick a cue near the end, set its correct time, and apply. Choose points with clear, short lines of dialogue, since long cues make it hard to see the exact start.
Fix sync that breaks after a cut or ad break
If the subtitles are perfect until a certain scene and then stay off by the same amount, something was cut from or added to the video at that point. A recap, a studio logo or a removed scene are the usual causes.
The fix is a partial shift:
- Find the first cue that is out of sync. That is where the edit happened.
- Measure the offset at that cue, the same way as in the constant delay section.
- In Subtitle Edit, select that cue and every cue after it, then use Adjust all times on the selected lines only.
- If the video has several cuts, repeat for each section, working from the start of the file to the end.
If you prefer to edit by hand, our guide on how to edit an SRT file covers the timestamp format and the mistakes that break a file.
Subtitles out of sync on Netflix, Prime Video or Plex
On streaming services you cannot edit the subtitle file, so the fixes are on the playback side. Turn the subtitles off and on again, switch to another subtitle language and back, restart the app, or restart the episode from the beginning. If one title is always off on every device, report it to the service: the file itself is wrong and only they can replace it.
Plex and similar media servers are different, because they use the subtitle files you add. If an SRT you added is out of sync there, fix the file with the steps above and replace it in the library folder. A player-level offset will not follow the file to other devices.
Check the file after you fix it
Shifts and frame-rate changes can leave small problems behind: cues that now overlap, a first cue pushed to 00:00:00, or lines that flash past too fast after a frame-rate change. Run the result through the free subtitle checker before you use it. It lists overlapping cues with both cue numbers, and flags very short or long cues, long lines and fast reading speed. It runs in your browser too.
If your player or platform needs a different format, convert the fixed file with the subtitle converter. Converting SRT to VTT keeps the same times; it does not fix sync on its own, so always fix timing first.
Translating a file after you fix the timing
Fix the sync before you translate, not after. Once the original file is right, a translation that keeps each cue's timing will be right too. Aivently's subtitle translator translates SRT, VTT and ASS files cue by cue and keeps the original timestamps, so the synced timing carries over to every language. You can preview the first 20 cues for free without signing up, and your first 10 minutes are free once your email is verified.
FAQ
How do I permanently fix subtitles out of sync in VLC?
VLC's G and H keys and the Track Synchronization panel change timing only during playback. To make the fix permanent, note the delay that works in VLC, then apply that offset to the SRT file with a sync tool or Subtitle Edit and save the new file.
Why do my subtitles get more out of sync as the movie goes on?
That pattern is drift, and it usually means the subtitles were timed for a different frame rate, such as 23.976 fps subtitles on a 25 fps video. A frame-rate conversion fixes it. If no standard pair works, use a two-point sync.
Can I sync subtitles online for free?
Yes. Free browser tools can shift every cue by an offset and convert between common frame rates. Aivently's subtitle sync tool does both and processes the file in your browser without uploading it.
How do I make subtitles appear earlier?
Shift the cues by a negative number of seconds. For example, enter -1.5 to show every line one and a half seconds sooner. Check the first cue afterward, since a large negative shift can push it to 00:00:00.
Does converting SRT to VTT fix sync problems?
No. Converting between SRT and VTT keeps the same start and end times, so an out-of-sync file stays out of sync. Fix the timing first, then convert.