FLT File

What are FLT files and how to open them

Are you having problems opening a FLT file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your FLT files.

What is a FLT file?

FLT files have multiple uses, and ESS-Code Filter is one of them. Read more about the other uses further down the page.

ESS-Code Filter

We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

How to open FLT files

Important: Different programs may use files with the FLT file extension for different purposes, so unless you are sure which format your FLT file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested ten different FLT openers which you will find listed below.

Last updated: August 6, 2026

All known file formats using extension .FLT

While ESS-Code Filter is a popular type of FLT-file, we know of 8 different uses of the .FLT file extension. Different software may use files with the same extension for different types of data.

Microsoft Flight Simulator Save File

The Microsoft Flight Simulator Save File (.FLT) format is a text-based configuration file used by Microsoft Flight Simulator (especially 2020 and 2024 versions) to store state information defining how a flight is set up when it is launched. It records details like aircraft position, systems on/off status, livery, weather, start point, mission or free flight mode, camera settings, and other flight-parameters. Its purpose is to let the simulator start a flight with all those parameters already applied - whether it's coming from a saved flight or an aircraft developer setting up the aircraft for different stages (e.g. apron, taxi, cruise) of its usage.

Files are produced by Microsoft Flight Simulator's save system when a user saves their current flight state, including aircraft choice, time of day, weather, system configuration etc. They use the .FLT extension, are editable in any text editor, and follow CFG-style structure with named sections like [Main], [Options], [SimVars.N] etc. Aircraft developers also create a suite of FLT files named for flight phases (apron.flt, climb.flt, final.flt, etc.) to define default states for those phases. These files live alongside the aircraft's main configuration files.

The .FLT file begins with a "[Main]" section with required metadata fields like Title, Description, AppVersion (the version of the sim it's designed for), MissionType (FreeFlight, Tutorial, etc.). Later sections define options, weather presets, camera settings, and one or more [Sim.N] entries describing individual simulation-objects (aircraft, AI elements) including their system states such as throttle, flaps, nav frequencies, etc. Paths within the file are relative to its folder.

FLT opener for Windows

We have identified one FLT opener that is compatible with this specific type of FLT file.

OpenFlight 3D File

We know that one FLT format is OpenFlight 3D File. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Qimage Filter

Qimage Filter (.flt) files are small, plain-text buddy files created by the Windows program Qimage Ultimate. Each .flt serves as an associative filter: it records a series of editing or print settings that are applied every time Qimage displays or prints the related image. The original image file remains untouched; the filter file defines how to adjust brightness, exposure, color, contrast, curves, noise reduction, sharpness and other visual settings. These filter files are useful when you want to maintain the original image and later tweak or review the edits at any time.

When you edit an image in Qimage using the Image Editor and choose "Associate" instead of "Create New Images", Qimage writes the .flt file in the same folder as the photo (or in its export location when applicable). Qimage shows which images have filters by marking the file name in red under thumbnails. Prints or screen display always use the original image plus any associated .flt settings. If you want to make edits visible outside Qimage, you can export or save a new image with the filter applied.

The contents of a .flt file begin with a header string such as V2003.10, followed by ASCII text fields listing numeric parameters (often in scientific notation), Boolean flags (TRUE/FALSE), named options (MEDIUM, NONE), font names (MS SANS SERIF), and other settings. Recognizable strings include "V2003.10", "0.00000000000000E+0000", "1.00000000000000E+0002", "MEDIUM", "MS SANS SERIF" and "FALSE". The file signature starts at offset 0 with ASCII "v2003.10…0" and contains repeating zero-filled blocks in later offsets.

Programs that open these FLT files

We have identified one FLT opener that is compatible with this specific type of FLT file.

Syntrillium CoolEdit Filter

We know that one FLT format is Syntrillium CoolEdit Filter. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Their Finest Hour: The Battle Of Britain Mission

We know that one FLT format is Their Finest Hour: The Battle Of Britain Mission. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Thermicroscopes SPMLab FP Data

We know that one FLT format is Thermicroscopes SPMLab FP Data. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

WinMerge Directory And File Filter

WinMerge Directory And File Filter (.flt) files define rules for including or excluding files and folders when comparing folders in WinMerge. They let you build filtering logic that is more precise than simple file masks, allowing you to limit the set of items shown or processed during a folder‐comparison operation. These filters are created by users or come with WinMerge as predefined templates, and they are stored in text format.

WinMerge creates these files when you use the Filters feature under folder comparison, or by saving a filter via the Filters dialog. When you choose a filter file in WinMerge (rather than entering a file‐mask), WinMerge reads the rules from the .flt file to decide which files and directories to skip or include in its comparison results. You'll often modify or copy template filter files (for example FileFilter.tmpl) to build your own .flt files. During folder comparison, items marked by the rules are either hidden by default or shown only if you enable skipping‐items display.

The format is plain text. Lines may start with rule prefixes like name, desc, def (defining whether rules define an include‐or‐exclude filter), or contain regular expression rules for files (f:) or directories (d:), with optional negation (f!:, d!:). Comments begin with "##". The file typically begins with a header signature "## This is a directory/file filter for WinMerge".

Programs that open these FLT files

We have identified one FLT opener that is compatible with this specific type of FLT file.

Various apps that use files with this extension

These apps are known to open certain types of FLT files. Remember, different programs may use FLT files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about FLT file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.