Free online SMI to SRT converter

A media player, editor, or subtitle platform may accept SRT files but not SAMI subtitles. Converting an SMI file produces a more widely supported text subtitle that can be edited, shared, or loaded beside a video.

What the SMI format is

In video subtitles, SMI refers to SAMI (Synchronized Accessible Media Interchange), a Microsoft caption format stored as an HTML-like text document. An SMI file commonly contains <SYNC Start="..."> elements with caption start times in milliseconds, <P> caption elements, optional language classes, and sometimes CSS formatting.

SAMI was used in older Windows Media captioning workflows and by subtitle-authoring applications. It can still appear in subtitle archives, older video releases, and collections containing multiple language tracks. The .smi extension has other meanings outside video subtitles, but those files are not suitable for this conversion.

What the SRT format is

SRT is a plain-text subtitle format. Each caption block contains a sequential number, a start and end time, caption text, and a blank line, for example:

1
00:01:12,500 --> 00:01:15,200
Caption text.

SRT timestamps use HH:MM:SS,mmm, with a comma before milliseconds. Most desktop video players, media servers, video editors, televisions, and subtitle tools support SRT. Its simple structure is easier to inspect and edit than SAMI's HTML-like structure and does not depend on a stylesheet.

How to convert SMI to SRT

Using 101convert

1. Open the SMI-to-SRT converter on 101convert.com. The conversion is available free without installing software.
2. Select or upload the subtitle file ending in .smi.
3. Start the conversion and wait for the SRT file to be generated.
4. Download the resulting .srt file.
5. Open the SRT in a text editor or subtitle application and check its captions and timing before using it with the video.

Using Subtitle Edit

1. Open the SMI file in the desktop application Subtitle Edit through File → Open.
2. If the file contains multiple language classes, confirm that the imported captions are in the intended language. Remove duplicate or unwanted tracks if necessary.
3. Export or save the subtitles through File → Save as, select SubRip (*.srt), and choose UTF-8 when an encoding option is offered.
4. Reopen the saved SRT and preview it with the video to verify synchronization and character rendering.

For confidential subtitle files, use a desktop application instead of uploading the file to a website.

Quality and compatibility considerations

SAMI and SRT both represent subtitle times with millisecond precision, so a normal conversion does not require the video's frame rate. SAMI may specify only a caption start time; the converter generally uses the next synchronization point, or another available timing rule, to create the SRT end time. A source with incorrect timings, a fixed delay, or timings for a different video cut will remain out of sync after conversion.

SRT cannot reliably preserve SAMI CSS, font declarations, colors, positioning, layout, or other document-level styling. Basic emphasis may survive as tags such as <i>, but complex presentation must be recreated in the player or video editor.

Inspect the output for missing captions, repeated lines, broken HTML entities, and incorrect characters. If accented or non-Latin text is corrupted, reopen the SMI using the correct source encoding and export the SRT as UTF-8. For automatic subtitle loading, give the SRT the same base name as the video, such as movie.srt beside movie.mp4.