What is the SMIL file format?
A .smil file is a text file containing markup written in the Synchronized Multimedia Integration Language (SMIL, pronounced "smile"). SMIL is used for creating multimedia presentations and slideshows that coordinate multiple media streams on a timeline. SMIL files contain references to audiovisual materials used in the presentation rather than the media itself - a .smil file alone carries no audio or video data.
SMIL files define presentation settings including animations, transition effects, layout, timings and embedded objects. Playback elements are organized into timing containers: <par> for parallel playback and <seq> for sequential playback of referenced audio, video, image and text clips. The SMIL format is also widely used as the basis for the MMS multimedia message format in mobile telephony (3GPP SMIL profile), as well as for DAISY digital talking books.
The SMIL specification was standardized by the W3C. SMIL is closely related to HTML, and SMIL files use XML markup to describe multimedia content, layout regions and synchronization. The current published version of the specification is SMIL 3.0 (W3C Recommendation, December 2008). SMIL timing concepts also live on inside SVG animation (<animate> derives from the SMIL timing model).
In modern web development, HTML5 <audio> and <video> elements with CSS/JavaScript have largely replaced SMIL for browser-based presentations, but the format remains in use in specialized players and broadcasting workflows.
Security & safety
RISK: LOWA SMIL file is small XML text and is not executable, so it carries little direct risk. The only caution: it can reference remote URLs, so opening an untrusted SMIL in a networked player could fetch external content. Inspect the XML in a text editor first if the source is unknown. The referenced media files (not the SMIL) are where any real payload would be.
Format details
in a nutshell- DAISY Digital Talking Book navigation - Accessible audiobooks (DAISY 2.02/3) use SMIL files to synchronize recorded narration with the text.
- Digital signage / IPTV playlists - Players such as those for BrightSign and some IPTV/STB systems use SMIL to schedule looping media on screens.
- MMS multimedia message layout - Picture/video text messages (3GPP MMS) embed a SMIL slide describing layout and timing of the message parts.
Programs that open SMIL files
Windows4 apps
RealPlayer
Freemium Open with RealPlayer if the SMIL references RealMedia (.rm/.ram) content; legacy support only. 
Ambulant Player
Open-source Open the .smil with File > Open; AMBULANT is the reference SMIL 3.0 player. Keep the referenced media files in their relative paths. 
Any text editor (Notepad++ / VS Code)
Open-source Open the .smil as text to read the XML and locate the media files it references.
Web browser (Firefox / Chrome)
Free Drag the .smil into a browser tab to view the XML source (browsers do not render SMIL timing, but show the structure). 
macOS2 apps
Linux2 apps
Technical details
deep spec| Format | XML text document |
| MIME type | application/smil+xml (also application/smil) |
| Encoding | UTF-8 (or any encoding declared in the XML header) |
| Root element | <smil> with namespace http://www.w3.org/ns/SMIL (SMIL 3.0) or earlier W3C SMIL namespaces |
| Timing containers | <par> (parallel), <seq> (sequential), <excl> (exclusive) - orchestrate overlapping or sequential media playback |
| Specification versions | SMIL 1.0 (1998), SMIL 2.0 (2001), SMIL 2.1 (2005), SMIL 3.0 (2008, current W3C Recommendation) |
| Typical file size | 1 KB - 50 KB (a timing/layout document only; contains no media data) |
| Compression | None in the file itself; may be gzip-compressed in HTTP transfer |
| Media content | None - references external audio, video, image and text files by URI |
| SMIL profiles | SMIL Basic, SMIL Mobile Profile (3GPP MMS), SMIL Tiny; each targets a specific player class |
| MMS usage | 3GPP SMIL Mobile Profile defines the multimedia message format used in mobile MMS messaging |
| SVG relationship | SVG animation elements (<animate>, <animateTransform>) derive from the SMIL timing model |
| Released | SMIL 1.0 - W3C Recommendation, June 1998 |
| Latest version | SMIL 3.0 - W3C Recommendation, December 1, 2008 (republished December 2008) |
| Open standard | Yes · royalty-free |
| Specification | www.w3.org |
SMIL conversions
Community Q&A
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