What Is an SRT File?

The SRT format is so simple you can write one by hand. Here is a complete, valid SRT file with three subtitle blocks:

1
00:00:00,000 --> 00:00:03,500
Welcome to the tutorial.

2
00:00:03,600 --> 00:00:07,200
Today we're going to talk about
how SRT files work.

3
00:00:07,300 --> 00:00:11,000
Let's start with the basic structure.

Each block follows the same rules:

1. Line 1 — Sequence number. Starts at 1 and increments by 1 for each subtitle. Some players ignore the number; others require strict ordering.
2. Line 2 — Timecode. The format is HH:MM:SS,mmm --> HH:MM:SS,mmm. Note the comma (not period) separating seconds from milliseconds — this is a hard rule of the SRT format. Hours, minutes, seconds are always two digits; milliseconds are always three.
3. Lines 3+ — Subtitle text. One or more lines of text shown together.
4. Blank line. Separates one block from the next. The file should end with a blank line.

That's the entire format. There are no headers, no metadata, no styling tags in standard SRT. Some video players accept basic HTML-like tags inside the text (<b>, <i>, <u>, <font color="...">) but these are extensions, not part of the original spec.

An SRT file is plain text — you can open it with any tool that opens text files. But for actually using the subtitles with a video, the workflow depends on what you're trying to do.

Open as text (read or edit)

• Windows: Right-click the .srt file → Open with → Notepad. Or use VS Code, Notepad++, or any text editor.
• macOS: Right-click the .srt file → Open With → TextEdit. Or use VS Code, Sublime Text, BBEdit.
• Linux: cat filename.srt in terminal, or open in gedit, nano, vim, VS Code.

If TextEdit on Mac shows garbled characters, the file may not be UTF-8. Open it with a more capable editor like VS Code, which auto-detects encoding.

Open with a video (play with subtitles)

• VLC Media Player (free, all platforms): Open the video in VLC, then drag the .srt file onto the playing video. Or use Subtitle → Add Subtitle File.
• QuickTime Player (Mac): Can't load a separate .srt file; it only shows subtitle tracks built into the video. Use VLC instead.
• YouTube: In YouTube Studio, go to Subtitles, pick the video, then Add → Upload file → select the .srt.
• Vimeo: Open the video in your library, click Languages, click the + icon, and pick the .srt file. Vimeo accepts SRT and WebVTT, and recommends WebVTT.
• Premiere Pro / Final Cut / DaVinci Resolve: File → Import (or drag onto timeline as captions track).

For a desktop player such as VLC to load the SRT automatically, give it the same name as the video file (e.g., my-video.mp4 + my-video.srt) and put it in the same folder.

You have three realistic options for creating an SRT file, in order of complexity:

1. Generate it automatically from a video (fastest)

If your video has speech, AI transcription tools can produce an SRT file directly. TranscribeVideo.ai takes a YouTube, TikTok, or Instagram URL and returns a transcript with timestamps; export the result as an SRT file. For local video files, tools like Whisper, Descript, Rev, or Otter can transcribe and export SRT in one step. This is by far the fastest method and the only realistic option for videos longer than a few minutes.

2. Write it by hand in a text editor

For a short clip (under 60 seconds) or for testing, hand-writing an SRT is fine. Open Notepad or TextEdit, follow the four-line block format above, and save the file with the .srt extension. Critical details:

• Save as UTF-8, not ANSI/Windows-1252. Non-English characters will break otherwise.
• Use commas, not periods, before milliseconds in timecodes.
• Include the blank line between blocks — many players will fail silently if it's missing.
• End the file with a final blank line.

3. Use a subtitle editor (Aegisub, Subtitle Edit, Kapwing)

For longer projects where you want precise timing control, a subtitle editor is faster than hand-writing. Aegisub (free, open-source, all platforms) and Subtitle Edit (free, Windows) are the most popular. They give you a waveform view, click-to-set-timestamp, and spell-check. For browser-based work, Kapwing's free SRT editor is good for short videos.

SRT looks simple but a handful of issues account for almost every "subtitles don't work" problem.

Subtitles appear out of sync

The video frame rate doesn't match what the SRT was authored against. If subtitles are slightly behind the audio and drift further over time, the video is probably 23.976 fps and the SRT was timed for 25 fps (or vice versa). VLC's Tools → Track Synchronization (or the G and H keys) shifts all subtitles by a fixed amount. That fixes a constant offset but not drift. For drift, use Subtitle Edit's Synchronization → Change frame rate tool.

Special characters show as garbled boxes or question marks

The file is saved in an encoding the player did not expect. The SRT format carries no encoding declaration, so players simply assume one — and modern players assume UTF-8, while older Windows tools often wrote Windows-1252. Open in VS Code, check the bottom-right corner for the encoding, and re-save as UTF-8 if needed. On Windows Notepad, use Save As → Encoding → UTF-8.

Subtitles don't appear at all

Common causes: (a) the .srt file isn't named the same as the video, (b) the file uses periods instead of commas in timecodes, (c) the file is missing blank lines between blocks, (d) the player doesn't support SRT (rare in 2026 but possible for embedded hardware).

Two lines of text become one long line

Some players ignore line breaks within a block. Use a player that supports multi-line subtitles (VLC, MPV) or merge to one line and trust the player's auto-wrap.

Inline tags (italics, bold) don't render

Standard SRT doesn't support styling. The HTML-like tags some players accept (<i>, <b>) are non-standard extensions. If you need styling, use a richer subtitle format like ASS/SSA or WebVTT.

SRT is the most-supported subtitle format but not the most capable. The two other formats you'll encounter:

WebVTT (.vtt)

The W3C subtitle format for HTML5 video (its spec is a W3C Candidate Recommendation). Browsers use it for the HTML <track> element. WebVTT is structurally similar to SRT but adds an explicit WEBVTT file header, supports CSS styling, has cue settings for position and alignment, and uses periods (not commas) before milliseconds. If you're embedding subtitles in a web page, you need WebVTT, not SRT. If you have an SRT file and need WebVTT, conversion is mostly text replacement (commas to periods, add the WEBVTT header).

SubStation Alpha / Advanced SubStation Alpha (.ssa, .ass)

The format used by anime fansubs and any subtitling that requires precise styling — different fonts, colours, positions, animations. ASS files are far more capable than SRT but only supported by a subset of players (VLC, MPV, mpv-based players). Overkill for most use cases; SRT remains the right choice unless you need styling.

When to pick which

If you're working with subtitles, you'll get SRT files from one of these sources:

• YouTube captions. Viewers can read a video's transcript on YouTube (Show transcript). Channel owners can download the caption file in YouTube Studio (Subtitles → Edit → Options → Download subtitles). Or use a YouTube transcript tool to get an SRT directly from a URL.
• AI transcription services. Tools like Whisper (open-source), Rev, Sonix, Otter, and TranscribeVideo.ai can export SRT as well as plain text. (For YouTube links, TranscribeVideo.ai builds the SRT from the video's own captions rather than from the audio.) On clear speech, AI transcription is now accurate enough that hand-correcting an AI-generated SRT is faster than transcribing from scratch.
• Professional subtitling services. 3PlayMedia, Rev, GoTranscript, and other paid services deliver human-checked SRT files for a per-minute fee.
• Existing video files. Many videos ship with embedded subtitle tracks. Tools like MKVToolNix and ffmpeg can extract text-based tracks: ffmpeg -i input.mkv -map 0:s:0 output.srt.
• Subtitle databases. Sites like OpenSubtitles host community-uploaded SRT files for popular movies and TV shows (legal grey area; check rights for your use case).