Skip to content

SMI to JSON Converter

Convert SAMI (SMI) subtitles to JSON (JSON) for free, right in your browser. No upload, no sign-up.

How it works

  1. 1

    Drop one or more files into the box above.

  2. 2

    Pick the output format (already chosen on dedicated pages).

  3. 3

    Download each file or everything as a ZIP. Nothing is uploaded.

About the formats

SMI (SAMI) is Microsoft's HTML-like caption format, still common for Korean subtitles and Windows Media.

JSON exports cues as structured data with times in milliseconds, for developers and automations.

Frequently asked questions

Is SMI to JSON Converter free?

Yes. Every tool on FastSub AI is free, with no sign-up, no watermark and no usage limits.

Are my files uploaded anywhere?

No. Your files are read and processed inside your browser tab. The only downloads are the app itself and, for AI tools, the model files.

Which subtitle formats are supported?

SRT, WebVTT, ASS/SSA, SBV, SUB (MicroDVD), SAMI, TTML/DFXP, LRC and CapCut projects in; all of those plus TXT, CSV, JSON, FCPXML, Word and PDF out.

Is there a file size limit?

Subtitle files up to 20 MB and videos up to several GB, limited only by your device's memory.

Related tools