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ASS, SSA, SRT and VTT subtitles

Change subtitle format or shift the timing of every cue. Use ASS, SSA, SRT and VTT subtitles locally with practical instructions, output settings and format limits.

A practical guide

ASS, SSA, SRT and VTT subtitles

Convert supported ASS, SSA, SRT and VTT cues into another subtitle format and shift their timestamps by a chosen number of seconds. Use it to fit a player’s accepted format or correct a consistent timing offset. Review cue text and synchronization because complex styling is not preserved through plain subtitle formats.

  • Convert SRT captions to WebVTT
  • Shift subtitle timing by a constant offset
  • Export ASS dialogue as plain SRT cues

How to use ASS, SSA, SRT and VTT subtitles

  1. Add the subtitle file

    Choose one ASS, SSA, SRT or VTT file with valid cues. Embedded subtitle attachments are unsupported, so use a text-based cue file without attached fonts or graphics.

  2. Choose the cue format

    Select SRT, VTT, ASS or SSA for the destination player. Expect plain or default styling rather than preservation of every source style and position.

  3. Set a timestamp shift

    Enter a positive shift to delay captions or a negative shift to move them earlier. Run the conversion after checking the sign of the intended adjustment.

  4. Review cues with the video

    Download the subtitle output and load it beside the intended video. Check early and late cues, line breaks and any timestamps affected by clamping at zero.

Understand the settings

Output format
Choose output format according to the result you need. Available choices: SRT; VTT; ASS; SSA. The initial selection is SRT.
Timestamp shift (seconds)
Timestamp shift (seconds) accepts values from -7200 to 7200, in increments of 0.1. The initial value is 0. Change it for a specific output requirement, then check the result before processing more files.

Captions for an HTML video player

A video has SRT captions that appear one second early. Select VTT and a positive one-second shift, then convert. Load the WebVTT file in the player and verify several spoken lines, including the first caption and a later cue.

Check your result

Upload a file, adjust settings and run the tool. All processing uses the local engine. ASS/SSA styling and positioning are lost in SRT/VTT. Negative timestamps are clamped to zero. Open the saved output in the app or workflow where you plan to use it. Check one representative result before repeating the same settings with more files. The original files stay unchanged.

What to know before you start

  • Files are processed on this device. Browser memory and engine-specific limits apply. Save results before reloading.
  • ASS/SSA styling and positioning are lost in SRT/VTT. Negative timestamps are clamped to zero.
  • Upload one file with a combined size of at most 100 MB. The completed output must fit within 200 MB.
  • Files are checked by the local engine; a matching filename alone is not proof of valid contents.
  • Selections and completed jobs stay available while you navigate inside this tab. Use My files to revisit results. Reloading or closing the tab clears the workspace; download results you want to keep first.

ASS, SSA, SRT and VTT subtitles: common questions

Which direction does a positive shift move captions?

A positive value adds time to each cue and makes it appear later. A negative value moves cues earlier. Check against spoken dialogue at several points to distinguish a constant offset from gradual synchronization drift.

What happens to negative timestamps?

Shifted timestamps below zero are clamped to zero. Moving early cues too far backward can therefore shorten or overlap their visible timing, so inspect the beginning of the converted subtitle file alongside the video.

Are ASS styles and positioning retained?

ASS and SSA styling and positioning are lost when exporting plain SRT or VTT cues. Outputs using ASS or SSA receive a default style rather than a complete reconstruction of the source’s elaborate subtitle presentation.

Does this translate subtitle text?

No. The operation converts cue structure and adjusts timestamps while keeping the dialogue text. Translation, correction of recognition mistakes and changes to the wording require a separate editing step before or after format conversion.

Does ASS, SSA, SRT and VTT subtitles upload files to another service?

Processing runs in this browser, on your device. Files and pasted input are not uploaded to a conversion server. The website and required engine assets must load first; large operations depend on available device memory.

Can I continue after changing pages?

Selections and completed jobs stay available while you navigate inside this tab. Use My files to revisit results. Reloading or closing the tab clears the workspace; download results you want to keep first.