AFM File

What are AFM files and how to open them

Are you having problems opening an AFM 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 AFM files.

What is an AFM file?

AFM files have multiple uses, and Adobe/Outline Font Metric is one of them. Read more about the other uses further down the page.

Adobe/Outline Font Metric

Adobe/Outline Font Metric is a plain-text font metrics file used with Adobe PostScript Type 1 fonts to store detailed layout information. It does not include the font outlines (the shapes of glyphs), only statistical data about how those glyphs should be spaced, positioned, kerned, and bounding-boxed.

The AFM file is produced alongside the font's outline files (usually .PFB or .PFA) by font foundries or font-creation tools. It is used by typesetting, page layout, printing, or font management software to determine global font metrics (such as font name, family, weight, cap height, ascender, descender, italic angle, underline position/thickness) and individual character metrics (like advance width, bounding box, character name) so that text can be laid out correctly. Tools reading AFM files use the information to compute how much horizontal space text occupies and where glyphs may overlap or need adjustment (kerning).

Technically the AFM format is ASCII-encoded and structured into sections. A correct AFM file begins with a line like "StartFontMetrics", contains sections delineated by keywords including "StartCharMetrics" / "EndCharMetrics" and includes fields such as FONTNAME, WX (width), C (character code), N (glyph name), B (bounding box), and optional kerning blocks. Byte signatures that identify AFM files include the ASCII header "StartFontMetrics" at the very beginning, and the presence of strings like "StartCharMetrics", "EndCharMetrics", and "FontName" somewhere in the file.

How to open AFM files

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

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

Last updated: August 17, 2026

All known file formats using extension .AFM

While Adobe/Outline Font Metric is a popular type of AFM-file, we know of 4 different uses of the .AFM file extension. Different software may use files with the same extension for different types of data.

Hitachi AFM Data

Hitachi AFM Data is a binary file format produced by certain Hitachi atomic force microscopes to store the raw height‐map measurements of a sample surface acquired during a scan. It captures the height value above each point in a regular 2D grid, which represents the surface topology that the AFM tip sensed.

These files are generated directly by Hitachi AFM instruments during or after a scanning measurement. Their typical workflow involves acquiring a raster‐scanned height field in both X and Y dimensions, then saving that data together with instrument settings and metadata. The files are intended for later processing in surface‐analysis software to view, correct, filter, measure features, and produce visualizations such as 3D models or contours.

One key feature distinguishing this format is its internal signature. The file begins with the ASCII magic string AFM/Ver… at the very start (offset 0), and somewhere in the initial section it contains the text "HITACHI AFM DATA VERSION".

Outline Font Metric

The Outline Font Metric format is a plain-text metric file used alongside PostScript Type 1 outline fonts. It does not contain the glyph outlines. The purpose of an AFM file is to hold font metric information such as each character's advance width, bounding box, kerning pairs, font bounding box, ascender, descender, and other layout-related values. Layout engines, printers and typesetting tools read this to determine spacing, alignment, and positioning of text when rendering or composing documents.

Adobe creates AFM files when distributing PostScript Type 1 fonts, especially in non-Windows or Unix environments. The font's outline data is in a companion file (often .pfa or .pfb), while the AFM file is used by applications that need detailed metrics without processing outline data. AFM files enable text layout calculations, kerning, and precise typesetting even before or without rendering the font outlines.

The format is ASCII-encoded and begins with the header keyword "StartFontMetrics", ends with "EndFontMetrics", and uses keywords like FontName, FontBBox, IsFixedPitch, and sections marked "StartCharMetrics" / "EndCharMetrics" for glyph-by-glyph data. Internal fields include values such as WX (width), C (character code), N (glyph name), B (glyph bounding box), ItalicAngle, UnderlinePosition, and UnderlineThickness.

Quesant AFM Data

Quesant AFM Data files store raw measurement data produced by Quesant atomic force microscopes for surface topography and related scanned surface measurements. These files encode both the recorded height values ("pixels") returned by the instrument's scanning probe and relevant scan settings such as physical pixel size, acquisition date, and device metadata. They are used when exporting data for analysis or processing in specialized software.

These files are created by Quesant Instrument Corporation's atomic force microscopy systems. Users generally export AFM images or height maps as .AFM files, which can then be read (but not written) by software that supports this specific format - examples include Gwyddion and Bio-Formats. Once imported, the pixel grid can be displayed, and height data manipulated or visualized.

The format supports numerous metadata fields. The Bio-Formats QuesantReader recognizes 22 metadata items including Image: AcquisitionDate, Description, Name, and ID; also pixel-size in X and Y, dimensions SizeX, SizeY, SizeZ, pixel bit-depth (Type, SignificantBits), and whether data are BigEndian or interleaved. PhysicalSizeX, PhysicalSizeY, SizeC, SizeT, dimension order and plane coordinates (TheC, TheT, TheZ) are also available.

On the file level, Quesant .AFM files begin with a specific 8-byte signature at offset zero: the bytes sequence 0x02 0x00 0x00 0x00 0x01 0x00 0x00 0x00 identifies this format. The header includes variables like date, comment, xSize (physical spacing), as well as an offset to the pixel height data (pixelsOffset) which follow the header.

Various apps that use files with this extension

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

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