What is the FST file format?
.fst is a binary preset file used by FL Studio (by Image-Line) to store the complete parameter state of a single synthesizer or effects plugin. The format shares the same chunked binary architecture as .flp FL Studio project files, but contains only one plugin's settings rather than an entire project.
The file begins with the FLhd (FL header) magic signature at offset 0, followed by an FLdt (FL data) chunk holding the serialized parameter values. When a preset targets a third-party VST plugin, the .fst file embeds the raw VST state blob alongside FL Studio's own parameter data.
Each .fst preset is tied to the specific instrument or effect it was saved from - a Sytrus preset is meaningless in Harmor or any other generator. FL Studio's built-in instruments (Sytrus, Harmor, Gross Beat, ZGameEditor Visualizer, and others) use .fst as their native preset format. Third-party VST 2 plugins use the cross-DAW .fxp format instead; VST 3 plugins use .vstpreset.
FL Studio stores presets in a Presets/ directory within the FL Studio data folder, organized by plugin name. The format is not publicly documented but has been partially reverse-engineered by the community.
Note: .fst is also the extension used by the OpenFst finite-state transducer library - an entirely unrelated binary format.
Security & safety
RISK: LOWBinary preset file; no script execution. Safe to open in FL Studio. Download presets only from reputable sources (Image-Line forums, Splice) to avoid ZIP-based malware disguised as preset packs.
Format details
in a nutshell- OpenFst binary FST file - OpenFst (Google/Johns Hopkins) finite-state transducer library saves compiled transducers as .fst binary files - entirely unrelated to audio.
Programs that open FST files
Windows1 app
FL Studio
Paid Right-click the target plugin in FL Studio → Presets → (browse) → select .fst file. Or place file in the plugin's preset folder and it appears in the preset list. 
macOS1 app
FL Studio (macOS)
Paid Same as Windows; FL Studio macOS supports FST presets from the same preset browser. Technical details
deep spec| Magic bytes | `FLhd` (46 4C 68 64) at offset 0 |
| Second chunk signature | `FLdt` (FL data chunk) |
| Byte order | Little-endian |
| Container structure | `FLhd` header chunk followed by `FLdt` data chunk |
| VST state embedding | Raw VST 2 plugin state blob embedded within `FLdt` when preset targets a VST plugin |
| Typical file size | 260 B - 110 KB (median ~3 KB) |
| Scope | Single plugin instance state - one generator or effect per file |
| Plugin binding | Preset is tied to the specific plugin it was saved from; not transferable between different plugins |
| Cross-DAW portability | None - FL Studio only; `.fxp` for VST 2 portability, `.vstpreset` for VST 3 |
| Operating systems | Windows, macOS |
| Storage path | `Presets/` subdirectory within FL Studio data folder, organized by plugin name |
| Released | c. 2000 (FL Studio, formerly FruityLoops) |
| Latest version | FL Studio 21 (2023); format internally versioned |
| Specification | www.image-line.com |
FST conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about FST files.
