Convert SRT to ASS Online

How to convert SRT to ASS

Converting takes a few seconds and never involves a server. Follow these steps:

1. Drop your SRT file — Drag the .srt file onto the box above, or click to browse. The file is read on your device and never uploaded.
2. Confirm the detected encoding — The format and text encoding appear as badges. Chinese and Japanese subtitle files saved on Windows are detected automatically so nothing comes out garbled.
3. Shift the timing if needed — If the source subtitles are out of sync, enter a Time shift in seconds before converting so you only have one file to correct.
4. Convert — Click Convert to ASS. The tool builds a valid ASS script with a script header, a default style definition and one dialogue line per cue.
5. Open in Aegisub and style — Download the .ass file and open it in Aegisub or any ASS-aware editor. Apply your fonts, colours, positioning and effects from there.

What is a SRT file?

SRT (SubRip Subtitle) is the plainest and most universal subtitle format. A cue is a sequence number, a start --> end timestamp line using a comma for milliseconds, one or more lines of text, and a blank line. There is no styling, positioning, actor field or karaoke support. Because of that simplicity, SRT is the format you will most often receive from subtitle sites, transcription services and caption exports, and it opens in essentially every player and editor.

What is a Advanced SubStation Alpha file?

ASS (Advanced SubStation Alpha) is a script-based subtitle format built for styled output. A file contains a [Script Info] section with resolution and playback metadata, a [V4+ Styles] section defining named styles (font, size, primary and outline colours, bold, italics, borders, shadows, alignment) and an [Events] section with the dialogue lines. Each line can carry override tags such as \pos for exact placement, \move for motion, \fad for fades and \k for karaoke. It is the standard for anime fansubbing, karaoke and any project where the visual presentation matters.

SRT vs ASS: what actually changes

Here is exactly what the conversion alters and what it preserves, so there are no surprises when you play the result:

Why convert SRT to ASS?

ASS is the format of choice for anime fansubs and for anyone who wants styled subtitles: it supports custom fonts, colours, precise on-screen positioning and even karaoke timing, none of which SRT can store. Converting SRT to ASS gives you a valid .ass file with a sensible default style applied, ready to refine in an editor. The text and timing from your SRT are carried across exactly.

Common use cases

Anime and fansub projects

Fansubbing workflows standardise on ASS because signs, karaoke and styled dialogue all need formatting that plain SRT cannot express.

Adding custom fonts and colours

Once in ASS, you can pick a typeface, set primary and outline colours, add a shadow and position text anywhere on the frame.

Karaoke and lyric subtitles

Syllable-level timing with \k tags is only possible in ASS, making it the required format for karaoke and lyric videos.

Positioning translations and signs

When a subtitle must sit next to on-screen text rather than at the bottom, ASS positioning is the tool for the job.

Tips and troubleshooting

Treat the default style as a starting point

The converter applies a clean, readable default style. Open the file in Aegisub and adjust the font, size and colours to match your video.

Set the video resolution in Script Info

ASS positioning assumes a specific frame size. If your video is not the default, update the PlayResX and PlayResY values before positioning cues.

Keep your SRT master

If anything goes wrong while styling, the original SRT is the clean source to re-convert from.

Not every player renders ASS styling

Desktop players such as VLC and MPC-HC handle ASS well; some phones and smart TVs do not. Keep an SRT copy for maximum compatibility.

Naming your subtitle files so players find them

Most desktop and mobile players load a subtitle file automatically when two conditions are met: the subtitle sits in the same folder as the video, and both files share the same base name. A video called movie.mp4 is matched by movie.srt, movie.en.srt or movie.en.forced.srt, but not by subtitles.srt or movie (1).srt. The language code in the middle is optional and is used by players that offer a subtitle track menu.

If captions do not appear, the problem is almost always the file name rather than the file contents. Rename the subtitle to match the video exactly, or use the player's subtitle menu to load it manually once. On macOS, Total Video Player Pro goes a step further and matches subtitle files to your video automatically, including subtitle tracks already embedded inside MKV and MP4 files.

Using the converted ASS file

The .ass file is meant to be opened in a subtitle editor, most commonly Aegisub. Start by opening your video in the editor, then load the .ass and check that the dialogue lines up. From there you can edit the default style — font, size, primary and outline colours, bold, italics, border and shadow — and any change applies to every cue using that style.

Before positioning anything, confirm the PlayResX and PlayResY values in the Script Info section match your video's resolution: ASS positioning is calculated against that frame size and will be wrong if it does not. Desktop players such as VLC and MPC-HC render ASS styling well, while some phones and smart TVs ignore it, so keep your original .srt alongside for maximum compatibility.

Privacy: nothing leaves your browser

Most online subtitle converters work by uploading your file to a server, processing it there and letting you download the result. That approach has three practical drawbacks: your subtitle text passes through someone else's machine, you wait for the upload and the download, and the service can impose file size limits, queues or watermarks.

This converter does none of that. It is built with JavaScript and runs inside your browser tab. When you drop a SRT file, the browser reads it from your disk, parses it in memory, converts it to ASS and hands the result straight back to you — no network request ever carries your content. That has a useful side effect: there is no queue, no server-side size limit and no watermark, and the tool keeps working even if you lose your connection after the page has loaded. If you handle unreleased footage, confidential transcripts or anything you would rather not share with a third party, local processing is the safer default.

Frequently asked questions