ASS vs SRT: Styled Subtitles and Plain Subtitles, Side by Side

ASS vs SRT at a glance

Structure

SRT is a list of numbered cues; ASS is a script with sections for settings, style definitions and events

Timing

SRT uses hours:minutes:seconds,milliseconds; ASS uses hours:minutes:seconds.centiseconds, so its steps are 10 ms

Styling

SRT has none in the standard; many players accept simple italic, bold, underline and font colour tags. ASS defines full named styles

Positioning

SRT has none in the standard; ASS has alignment, margins and exact pixel positions

Effects

ASS supports fades, movement, rotation, karaoke syllable timing and vector drawings; SRT has none

Readability

SRT is easy to read and edit in any text editor; ASS is readable but dense

Support

SRT is accepted almost everywhere; ASS is rendered fully by desktop players such as VLC and mpv, partly or not at all by many TVs, sticks and platforms

The same subtitle in both formats

Seeing one cue written both ways explains most of the difference. In SRT, a line of dialogue is three lines of text followed by a blank line:

Cue number

12

Timing

00:01:04,250 --> 00:01:07,100

Text

Don't open that door.

In ASS, the same line sits inside a script. The style is defined once and every Dialogue event refers to it by name:

[Script Info]

PlayResX: 1920 and PlayResY: 1080 set the canvas that positions and sizes are measured against

[V4+ Styles]

Style: Default,Arial,64,&H00FFFFFF,&H000000FF,&H00000000,&H64000000,0,0,0,0,100,100,0,0,1,3,1,2,40,40,60,1

[Events]

Dialogue: 0,0:01:04.25,0:01:07.10,Default,,0,0,0,,Don't open that door.

The style line packs font, size, colours, bold and italic flags, outline and shadow, alignment (2 means bottom centre) and margins into one comma-separated row; colours are written as &H followed by alpha, blue, green and red. Because the Text field is last, it can itself contain commas. A line break inside ASS text is written as \N, where SRT simply starts a new line.

What ASS can do that SRT can't

• Several styles in one file. Dialogue in white at the bottom, a narrator in italics, on-screen signs in a typeface that matches the sign.
• Exact placement. An override tag such as {\an8} moves a line to the top centre; {\pos(960,80)} places it at specific coordinates on the script's canvas, so a translation can sit next to the sign it translates.
• Timed effects. Fades in and out, movement across the screen, rotation and colour changes over time.
• Karaoke. Tags such as {\k25} give each syllable its own duration, so song lyrics fill in as they're sung.
• Layers and drawings. Lines can stack in layers, and vector shapes can draw boxes or masks.

SRT's limits are also its strength: with nothing to render except text, every player shows it the same basic way, and anyone can fix a typo in Notepad.

Where each format works

Support for ASS is the deciding factor more often than features. Here is what the official documentation of a few common destinations says:

• YouTube. Its help page lists SubRip (.srt) as a basic format, supported only in plain UTF-8 with no style markup recognised. ASS isn't on the list of accepted files; for positioning, YouTube points to formats such as WebVTT and TTML.
• Plex. Lists SRT, SMI, SSA/ASS and WebVTT as fully supported, embedded or as sidecar files.
• TVs. LG lists ass and ssa among external subtitle formats for USB playback and Sony's BRAVIA Help Guide lists SSA/ASS, but listing a format doesn't guarantee full styling. Roku Media Player only picks up .srt and .vtt sidecars, as described in the guide to Roku Media Player subtitles.
• Desktop players. VLC and mpv render ASS with its styling, which is why fansubbed releases are made for them.
• Video editors. Most accept SRT for caption tracks; ASS import varies widely, so check your editor before relying on it.

If your choice is really between SRT and WebVTT for the web, that comparison has its own page: SRT vs VTT. The wider family of formats, including TTML and image subtitles, is covered in subtitle file formats.

What happens to ASS styling in each situation

• Played soft in a full ASS renderer. You see what the author designed, provided any fonts the script names are installed or attached to the MKV.
• Played soft in a limited player. The words usually appear in the player's default style, at the bottom, with positioned signs piled on top of dialogue, or the track is skipped.
• Converted to SRT. Text and timing survive; styles, positions, karaoke and drawings are gone.
• Burned into the video. The renderer draws every effect into the frames, so the result looks identical on any device, but it can't be turned off or changed. ffmpeg's subtitles filter renders ASS this way; the guide to burning subtitles with ffmpeg shows the commands.

Converting in either direction

ASS to SRT. The free ASS to SRT converter runs in your browser without uploading the file. It keeps the text and timing, drops styling and positions, skips drawing commands and comment lines and counts them in a note, and flags lines that were positioned on screen, which are usually signs you may want to keep, reword or delete.

SRT to ASS. The SRT to ASS converter writes the cues into a 1920 by 1080 ASS script with the style options you choose: font, size, colours, outline, margin and alignment. That gives every line one consistent style; for per-line positioning or karaoke, open the result in a dedicated ASS editor such as Aegisub.

Two examples

A middle path: styled, burned-in SRT

Many people want ASS mainly for a readable font, a background box or captions at the top. If that's all, you don't need ASS. The free subtitle editor imports an SRT or VTT (not ASS), applies one style to the whole video, with 8 presets, 19 fonts, colours, a background box and top, middle or bottom placement, and renders an MP4 with the subtitles burned in, in your browser on a computer. It can't do per-line positioning, karaoke or animated captions, so a fully typeset ASS file still needs a renderer such as ffmpeg.

Limits to keep in mind

• Converting ASS to SRT is lossy and can't be undone; keep the original ASS.
• An ASS file depends on fonts. A missing font falls back to another, which changes line widths and can push text off screen.
• ASS positions are measured against the script's canvas size, so a script made for one resolution may look misplaced if the canvas settings don't match the player's assumptions.
• SRT formatting tags are not standardised; a tag one player shows may appear as literal text in another.

Starting from scratch

If you don't have subtitles yet, the subtitle generator transcribes the audio into SRT or VTT in 100 languages for 1 credit per minute (minimum 5 credits per file), so a 12-minute video costs 12 credits (1.2¢). Only the audio is uploaded for the AI step and it's deleted within 30 minutes of the job finishing. Start from that SRT, then convert to ASS if you need typesetting.