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AI Subtitle Rewriter

Fast. Private. Perfect.

Improve naturalness, fix grammar, shorten, expand, simplify, or rewrite subtitle text conversationally using GPT models. Bring your own API key.

Private & Secure
Blazing Fast
Free & Unlimited

Drag & drop your subtitle file here

or click to browse

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

100% LocalNo UploadSecureInstant

How It Works

1

Upload your subtitle file.

2

Enter your OpenAI API key (get one at platform.openai.com).

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. The tool processes subtitle text in batches.

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.

Truly Unlimited

No file size limits. No daily limits. Completely free.

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.
Multiple GPT models: from GPT-4o mini (fast, affordable) to GPT-4o (highest quality).
Preserves all timing and subtitle structure - only the text is rewritten.
Your API key stays in your browser - never sent to our servers.

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. This tool uses your own OpenAI API key. You can get one at platform.openai.com. The key is stored only in your browser session and sent directly to OpenAI, 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).

Yes. AI rewriting only modifies the text content. All timestamps and subtitle structure are preserved exactly.

Cost depends on the model and number of cues. GPT-4o mini is very affordable (typically under $0.01 for a full movie). GPT-4o costs more but produces higher-quality rewrites.

Yes. Your subtitle file and API key are processed entirely in your browser. Rewrite requests go directly from your browser to the OpenAI API. 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 using GPT models. Bring your own API key.