How to Edit an SRT File (Mac, Windows, Online) 2026

An SRT is plain text, so any text editor can edit it — the catch is that fixing timing by hand is miserable, and one malformed timecode breaks the whole file. For typos, use a text editor. For retiming, use a subtitle editor with a video preview. For shifting every caption by the same amount, use one FFmpeg command.

Each job and the right tool for it.

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Job 1: Fixing Typos and Wording

The most common edit, and the easiest.

On a Mac with TextEdit:

1. Right-click the .srt → Open With → TextEdit.
2. If it opens as rich text, Format → Make Plain Text (Shift+Cmd+T).
3. Edit the text lines only. Leave the numbers and timecodes alone.
4. Save with UTF-8 encoding, keeping the .srt extension.

Better: use a code editor. VS Code, Sublime Text or BBEdit show line numbers, won't silently convert to rich text, and make encoding visible. VS Code also has SRT syntax highlighting extensions that make malformed timecodes obvious.

What to fix first: proper nouns, brand names, technical terms and numbers. Automatic transcription gets ordinary words right and those wrong, and those are the words that matter.

Don't touch: the sequence numbers or the --> arrows. Changing a number's order breaks strict parsers.

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Job 2: Retiming Individual Captions

Hand-editing timecodes against a video means playing, pausing, reading the time, and typing it. For more than two or three fixes, use a real subtitle editor.

Subtitle editors for Mac:

• Aegisub — free, powerful, ugly, and still the standard. Waveform view, video preview, keyboard-driven timing.
• Subtitle Edit — free and excellent, Windows-native but runs on Mac under Wine or a VM. The best waveform timing tools of any free option.
• Jubler — free, Java-based, cross-platform, simpler than Aegisub.
• Final Cut Pro / Premiere — if you already own one, importing the SRT and dragging caption blocks on a timeline is the most intuitive retiming interface available.

The workflow in any of them: load the video and the SRT together, find the caption that's off, drag its start or end against the waveform, save. Speech is visible in a waveform, so timing to it is far faster than timing to a video preview alone.

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Job 3: Shifting Every Caption by the Same Amount

The most common timing problem: the whole file is offset because the audio was trimmed after the transcript was made.

With FFmpeg — delay everything by 2.5 seconds:

ffmpeg -itsoffset 2.5 -i captions.srt -c copy shifted.srt

Bring everything 1.2 seconds earlier:

ffmpeg -itsoffset -1.2 -i captions.srt -c copy shifted.srt

In a subtitle editor: Aegisub has Timing → Shift Times; Subtitle Edit has a Synchronisation menu with both a constant shift and a two-point sync for files that drift.

If the file drifts — correct at the start, progressively wrong later — the frame rate is mismatched. That needs a two-point sync (set the correct time for the first and last caption, and let the tool rescale everything between), not a constant shift.

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Job 4: Reformatting Line Breaks

Automatic transcription produces captions that are technically valid and hard to read: 70-character single lines, or breaks in the middle of a phrase.

The targets:

• 32–42 characters per line
• Two lines maximum per caption
• Break at natural points — after punctuation, or before a conjunction or preposition, never mid-phrase

Compare:

I went to the shop and bought
milk

against

I went to the shop
and bought milk

Same content, and the second is measurably faster to read.

Doing it in bulk: Subtitle Edit has "Auto-balance lines" and "Split long lines" tools that apply the rules across an entire file. This is the single biggest quality improvement available on a machine-generated SRT and it takes seconds.

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Job 5: Merging and Splitting Captions

Splitting a caption that's too long: in a subtitle editor, place the cursor at the break point and use the split command — it divides the text and interpolates a timecode. Doing this by hand means inventing a timecode, renumbering everything after it, and usually getting it wrong.

Merging two captions that flash by too fast: select both and merge. The combined caption takes the first start time and the second end time.

Rule of thumb: minimum 1 second on screen, maximum about 7. Anything under a second can't be read; anything over seven should have been two captions.

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Job 6: Bulk Find-and-Replace

For a recurring error — a name transcribed wrong every time — use find-and-replace in a code editor.

One warning: never blind-replace a comma. SRT timecodes use commas before milliseconds, and a global comma replacement destroys every timecode in the file. Restrict replacements to whole words, or use a regex that excludes timecode lines.

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Validating After You Edit

Before you rely on the file:

1. Open it in VLC with the video (Subtitle → Add Subtitle File). VLC is forgiving, so failure there means real breakage.
2. Check the sequence numbers are still consecutive from 1.
3. Check encoding — accented characters showing as é means it wasn't saved as UTF-8.
4. Check the last caption — a truncated final block is a common result of an editor not adding a trailing newline.
5. Upload to YouTube as a validator. Its caption upload rejects malformed files with a specific error message.

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The Faster Alternative: Edit the Transcript, Not the File

For most people this whole article is solving a problem that shouldn't exist.

If you generate captions from a transcription tool, fix the text in the tool — where the words are linked to the audio and the timing updates itself — then export a correct SRT. Editing a transcript is fast; editing a subtitle file is not.

BlitzCut works this way on Mac: correct a word in the transcript, and the caption and its timing follow. So does Descript. The SRT becomes an export, not a document you maintain.

Hand-editing an SRT is the right move when someone sent you one, or when it's the only artifact you have.

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Frequently Asked Questions

What program opens an SRT file?

Any text editor — TextEdit on Mac, Notepad on Windows, VS Code anywhere. For timing changes, a dedicated subtitle editor like Aegisub or Subtitle Edit is far easier.

How do I fix subtitles that are out of sync?

If everything is off by the same amount, apply a constant shift with FFmpeg's -itsoffset or a subtitle editor's shift function. If the offset grows over the video, it's a frame-rate mismatch and needs a two-point sync instead.

Can I edit an SRT file on a Mac without extra software?

Yes. TextEdit works, provided you switch to plain text with Shift+Cmd+T and save as UTF-8. It's fine for typos and poor for timing.

Why did my SRT stop working after I edited it?

Most often: saved as rich text or the wrong encoding, a timecode comma replaced with a period, a missing blank line between blocks, or a broken sequence number. Open it in VLC to confirm and check the timecode lines first.

How do I change the font or colour in an SRT file?

You can't reliably — SRT has no styling in its spec. Styling either comes from the player, from WebVTT if you convert, or from burning the captions into the video. See SRT vs VTT vs SBV.

How long should each caption be on screen?

Between 1 and 7 seconds, at a reading speed of roughly 15–20 characters per second. A 60-character caption needs at least 3 seconds.

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Fix the word, not the timecode. BlitzCut AI links every caption to the audio, so correcting the transcript retimes itself — then exports a clean SRT or burns the captions in. Mac and iPhone.

Try BlitzCut AI free for 3 days

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Related: How to Create an SRT File on Mac · SRT vs VTT vs SBV · How to Burn Subtitles into Video on Mac · Caption Accuracy Comparison · Best Subtitle Generator for Mac

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Last Updated: August 23, 2026 Category: Subtitles & File Formats Topic: Editing SRT Files