Skip to content

AI Subtitle Rewriter

Fast. Private. Perfect.

Improve naturalness, fix grammar, shorten, expand, simplify, or rewrite subtitle text conversationally. Bring your own API key for OpenAI or an approved OpenAI-compatible provider.

Private & Secure
Blazing Fast
Free & Private

Drag & drop your subtitle file here

or click to browse

SRT, VTT, ASS, SSA, LRC, SBV, TTML, SCC, STL, SMI, TXT, JSON

100% LocalNo UploadSecureInstant

How It Works

1

Upload your subtitle file.

2

Choose OpenAI or an approved OpenAI-compatible provider, then enter your API key.

3

Choose a rewrite task: improve naturalness, fix grammar, shorten, expand, simplify, make conversational, or custom.

4

Select an AI model based on your quality and cost preferences.

5

Click Rewrite. Parsing happens locally, and cue text is sent in batches directly to your chosen provider.

6

Download the rewritten subtitle file in SRT, VTT, or TXT format.

Why Choose AllSubConverter?

Your Privacy Matters

Everything runs in your browser. Your files are never uploaded.

Lightning Fast

Optimized processing engine converts files in seconds.

Free & Local

Each file can be up to 50 MB. Batches can contain up to 200 files or 1 GB total.

Works Everywhere

Works on Windows, Mac, Linux, iOS, Android - any modern browser.

AI Rewrite Modes

Improve Naturalness: make dialogue sound more fluent and natural.
Fix Grammar: correct grammar, spelling, and punctuation errors.
Shorten: condense verbose subtitles into concise, readable lines.
Expand: add natural wording to overly terse or clipped subtitles.
Simplify: rewrite using plainer language and shorter words.
Make Conversational: rewrite in a natural, spoken tone.
Custom: follow your own instructions for any rewriting task.
Choose a built-in OpenAI model or enter a custom model ID for an approved OpenAI-compatible endpoint.
For SRT and VTT output, timing and cue structure are retained while the text is rewritten.
Your API key stays in memory for the session and is saved on this device only after you choose Remember.

Who Needs AI Rewriting?

Auto-Generated Captions

Improve speech-to-text captions that have awkward phrasing, missing punctuation, or run-on sentences.

Translation Polish

Fix grammar and improve the natural flow of machine-translated subtitles before publishing.

Accessibility Readability

Shorten overly long subtitle lines so they fit on screen and meet CPS readability standards.

Content Summaries

Generate a concise text summary of a video's subtitle track for descriptions or metadata.

Fansub & Localization

Expand terse translations into more natural, idiomatic subtitles for the target language.

Educational Content

Improve the clarity and grammar of subtitles in lecture videos and online courses.

Frequently Asked Questions

Yes. The tool connects with your own API key. You can use OpenAI or an approved OpenAI-compatible endpoint. The key is kept in memory for the session and sent directly to your chosen provider, never to our servers.

Seven tasks: Improve Naturalness (make dialogue fluent), Fix Grammar (correct errors), Shorten (condense), Expand (add natural wording), Simplify (use plainer language), Make Conversational (spoken tone), and Custom (follow your own instructions).

For SRT and VTT output, timestamps and cue structure are retained while the text is rewritten. TXT output contains the rewritten text without timing.

Cost depends on your provider, model, and number of cues. Check the provider's current pricing before running a large subtitle file.

Parsing and output generation happen locally. Rewrite requests, including cue text and your API key, go directly from your browser to the provider you choose. We never see or store your files or key.

Input: SRT, VTT, ASS, SSA, LRC, SBV, TTML, SCC, STL, SMI. Output: SRT, VTT, or TXT.

Ready to convert your subtitles?

Improve naturalness, fix grammar, shorten, expand, simplify, or rewrite subtitle text conversationally. Bring your own API key for OpenAI or an approved OpenAI-compatible provider.