About - Browser-Based Subtitle Tools
AllSubConverter is a browser-based subtitle toolkit with 117+ tools. Convert, edit, sync, and translate 11 core subtitle formats plus YouTube JSON3 input.
AllSubConverter started with a simple idea: subtitle tools should be fast, private, and easy to start. No signups or output watermarks — just open your browser and get to work. Today we offer 117+ tools spanning 11 core subtitle formats plus YouTube JSON3 input, designed for subtitle professionals, translators, developers, and language learners.
Our Core Values
Privacy First
Standard subtitle processing runs locally in your browser and does not upload files to our servers. AI tools send cue text directly from your browser to the provider you choose.
No Sign-up
No account, no email, no credit card. Open the site, pick a tool, and start working immediately.
Fast Local Processing
Local processing avoids file-upload and server-processing delays. Processing time depends on the file size and your device capabilities.
Free Core Tools
Built-in tools are free with no output watermarks. Standard limits are 50 MB per file, 200 files per batch, and 1 GB total per batch; AI tools require your own provider API key.
Engineering & Technical Architecture
How AllSubConverter achieves browser-based subtitle processing, client-side privacy, and format-accurate parsing.
Client-Side Processing Engine
Parsers, normalizers, and converters for standard tools run directly in your browser's JavaScript runtime and Web Workers. Standard subtitle files do not touch a remote backend or queue, eliminating server transfer delays.
Universal Encoding Detection
Legacy subtitles frequently suffer from mojibake (garbled characters) when encoded in regional charsets. Our engine uses statistical byte frequency analysis to auto-detect UTF-8, UTF-16, GBK, Big5, Shift-JIS, and Windows-1252 before parsing.
Format-Accurate Parsing
Each converter targets common structural conventions: SubRip timing syntax, W3C WebVTT cue payloads, ASS/SSA dialogue structures, YouTube SBV comma pairs, and SMPTE-TT/TTML namespaces. Format-accurate parsing does not replace recipient-specific delivery validation.
Automated Round-Trip & Regression Testing
Over 4,600 automated test cases cover parser edge cases, line endings, BOM markers, and round-trip conversion scenarios. These tests help detect timing drift, parsing errors, and unintended text loss during development.