What is the IMP file format?
An .imp file is a legacy import filter definition created by FileMaker Pro (now Claris FileMaker). It stores a saved field-mapping configuration that tells FileMaker how to match columns from an external data source - such as a CSV file, tab-delimited text, or spreadsheet - to fields inside a FileMaker database. By saving this mapping as an .imp file, users could reuse the same import configuration repeatedly without respecifying field assignments on each run.
The format is proprietary and binary, developed by FileMaker, Inc. (now Claris International, an Apple subsidiary) during the FileMaker Pro 3-4 era in the mid-1990s. No public specification exists, and the internal structure is tied to the FileMaker version that created it.
In modern Claris FileMaker Pro (version 19 and later), import mappings are handled through the Import Records script step with saved mappings, which largely replaces standalone .imp filter files. Legacy .imp files from older FileMaker versions may not load correctly in current releases.
Note: the .imp extension is also used by several unrelated programs, including Lotus Improv spreadsheets, Adobe Audition convolution presets, and Pascal compiler tools. Only the FileMaker meaning is described here.
Security & safety
RISK: LOWBinary configuration file; no executable content, no known malware vector. May contain field names and import path information.
Format details
in a nutshell- Lotus Improv spreadsheet file - Lotus Improv (discontinued 1996) used .imp for its spreadsheet format; a historic curiosity.
- Adobe Audition Convolution Effect Preset - Adobe Audition stores some convolution reverb presets with the .imp extension.
- IMP e-book format - IMP format used by the Hanlin eBook reader (iSilo/Imec) for e-books on early e-ink devices.
Programs that open IMP files
Windows1 app
Claris FileMaker Pro
Paid Import filters are loaded automatically when executing an Import Records script step that references the .imp file, or via File → Import Records and selecting the saved filter. 
macOS1 app
Claris FileMaker Pro
Paid Same as Windows - IMP files are used automatically by FileMaker import scripts. Technical details
deep spec| Format type | Binary configuration/filter file |
| Developer | Claris International (formerly FileMaker, Inc.), an Apple subsidiary |
| Encoding | Binary (proprietary) |
| Byte order | Likely big-endian (reflecting FileMaker's Mac-first heritage) |
| Typical file size | Less than 50 KB |
| Associated OS | Windows, macOS |
| Purpose | Stores field-mapping configuration for repeatable FileMaker data imports from CSV, Excel, or tab-delimited sources |
| Modern equivalent | Import Records script step with saved mappings (FileMaker 19 / Claris FileMaker Pro 2023+) |
| Related formats | .fmp12, .fp7 (FileMaker database files) |
| MIME type | application/octet-stream |
| Version compatibility | Legacy .imp files from older FileMaker versions may be incompatible with FileMaker 19 and later |
| Released | circa 1990s (FileMaker Pro 3-4 era) |
| Specification | help.claris.com |
IMP conversions
Community Q&A
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