Subtitle Timestamp Format Converter

The Subtitle Timestamp Format Converter takes the SubRip text you paste into the SRT Content box and rewrites every timecode using the character you pick in Millisecond separator. Input is plain SRT; output is plain SRT with identical text and timing, differing only in whether a stamp reads 00:01:23,480 or 00:01:23.480.

This sounds trivial until a delivery bounces. SubRip specifies a comma, but plenty of software does not follow it: WebVTT-oriented players, scripting pipelines and in-house validators often expect a dot, while broadcast and localisation vendors reject anything that is not comma-separated. Translators, YouTubers whose upload silently fails, e-learning teams and accessibility staff preparing 508 deliverables all hit this mismatch, usually minutes before a deadline.

The converter parses the file into cues rather than running a blind find-and-replace, so a comma inside dialogue is never touched. Each time is decoded to whole milliseconds and re-serialised as HH:MM:SS plus your separator plus three digits, so hours are zero-padded and short millisecond fields are normalised. Because the file is rebuilt from the cue list, indices come out in clean sequence and stray blank lines disappear. No rounding occurs, so the event schedule is unchanged.

Everything runs locally in your browser, so no caption text is uploaded. Feature-length files convert in well under a second and download with the .srt extension.

• Comma or dot output: The Millisecond separator select lets you emit either the SubRip standard comma or the dot form that many parsers and validators insist on. Switching direction is a single change, so you can convert the same file both ways for two different clients.
• Real parsing, not search and replace: The tool reads the file into structured cues before writing it back out, so commas and full stops inside the dialogue itself are left completely alone.
• Timing preserved exactly: Start and end points are decoded to whole milliseconds and re-encoded with no rounding, arithmetic or drift, so the converted file cues at precisely the same moments as the original.
• Timestamp normalisation: Short or irregular millisecond fields are padded to three digits and hour fields are zero-padded, producing stamps that strict validators accept.
• Automatic renumbering: Because the output is rebuilt from the cue list, subtitle indices come out sequentially from 1 even if the source had gaps or duplicates.
• Whole file in one pass: Every cue in the SRT Content box is converted at once, so there is no per-line editing and nothing gets missed in a long file.
• Download or copy: The finished text can be copied to the clipboard or saved as a .srt file ready to hand off.
• Runs entirely offline in the tab: Nothing is transmitted anywhere, which matters for embargoed shows and pre-release scripts.

1. Open the tool and paste your captions into the SRT Content box, or click Load sample first if you would rather see how a comma-to-dot conversion behaves before risking your own file.
2. Check which direction you need by looking at one timestamp in the source: 00:00:04,120 is comma style and 00:00:04.120 is dot style.
3. Set Millisecond separator to the character your target application expects, choosing the comma for standard SubRip delivery or the dot for tools that demand it.
4. Press Run to convert the whole file; the rewritten SRT appears in the output panel immediately.
5. Scan the first and last cues in the result to confirm the separator changed and that the hours, minutes, seconds and millisecond values are unchanged.
6. Copy the output to your clipboard, or download it as a .srt file and load it into your player or subtitle editor to confirm it opens cleanly.

Example 1 - a validator that rejects commas. A localisation vendor returns your file because their ingest expects dot-separated milliseconds. Paste the SRT, set Millisecond separator to the dot, and run.

Before:
1
00:00:01,000 --> 00:00:04,000
Welcome back to the show.

After:
1
00:00:01.000 --> 00:00:04.000
Welcome back to the show.

Example 2 - normalising a hand-edited file. Someone typed timings by hand and left ragged millisecond fields plus broken numbering. Converting back to comma style repairs both at once.

Before:
3
0:00:07.5 --> 0:00:09.25
It was closer than we thought.

After:
2
00:00:07,500 --> 00:00:09,250
It was closer than we thought.

The event times are identical in both cases; only the written form changes, which is exactly what a picky parser is complaining about.

• Deliveries stop bouncing: Matching the separator your client's validator expects removes one of the most common reasons a technically correct subtitle file is rejected on ingest.
• No risk to your timing work: Because nothing is recalculated, you can convert freely without worrying that carefully synced cues will shift by a frame.
• Minutes saved over manual editing: Replacing separators by hand across hundreds of cues is slow and error-prone; this does the whole file in one click.
• One file serves two pipelines: Keep a comma master for broadcast and generate a dot version for your scripting or QC toolchain whenever you need it.
• Confidential material stays on your machine: The conversion runs in the browser with no upload, so unreleased dialogue never leaves your computer.
• Cleaner files downstream: Padded milliseconds and resequenced indices mean fewer surprises in the next tool that touches the file.