Free online BDF to WOFF converter

A website or browser-based application may require a WOFF web font, while the available typeface exists only as a BDF bitmap font. Converting it requires packaging the font for web use and usually tracing its bitmap glyphs into scalable outlines.

What the BDF format is

BDF, or Bitmap Distribution Format, is a human-readable text format for bitmap fonts. Each glyph stores a pixel matrix, character encoding, advance width, and other metrics for one or more fixed pixel sizes.

BDF files are common in the X Window System, terminal environments, embedded displays, and Unix font development. Font editors and utilities such as FontForge can create or export them; projects such as GNU Unifont also distribute BDF files. BDF is encountered when a font must preserve the exact pixels of a low-resolution display rather than scale smoothly.

What the WOFF format is

WOFF, or Web Open Font Format, packages an OpenType or TrueType font for use with CSS @font-face. It supports compression, metadata, Unicode mappings, and the font tables used by modern browsers.

WOFF is suitable for serving a typeface from a website without requiring users to install the source font. It is usually smaller than an uncompressed desktop font, but it does not automatically convert bitmap glyphs into scalable outlines. WOFF2 is generally smaller than WOFF, although a site may specifically require the older WOFF format.

How to actually convert BDF to WOFF

FontForge is the most practical desktop tool for this conversion because it can open BDF, convert bitmap glyphs to outlines, and generate WOFF.

1. Install FontForge and open the .bdf file with File → Open.
2. Check the glyph set, encoding, pixel size, advance widths, and family name. Correct missing Unicode assignments before generating the web font.
3. Select the glyphs and use Element → Autotrace to turn bitmap glyphs into vector outlines. Autotracing is normally required for broad browser compatibility; the result will not be an exact pixel-for-pixel representation of the BDF.
4. Review representative glyphs at several zoom levels. Remove accidental contours, repair disconnected shapes, and check that punctuation and accented characters have correct side bearings.
5. Use File → Generate Fonts, choose WOFF as the output format, select an output filename such as font.woff, and generate the file.
6. Serve the result with a matching CSS rule, for example @font-face { font-family: 'ConvertedFont'; src: url('font.woff') format('woff'); }. Test the font in the browsers and font sizes used by the website.

The built-in converter on 101convert.com can also convert the file for free without installing software. Verify its output carefully, because an automatic service may preserve a bitmap font, choose a different tracing method, or alter naming and Unicode metadata.

Quality, compatibility, and limitations

The main limitation is the difference between the formats: BDF records fixed-resolution pixels, while a web font is normally expected to provide scalable outlines. Autotracing can create jagged corners, excessive nodes, uneven stroke widths, and poor small-size rendering. Manual cleanup in FontForge may be necessary for a professional result.

If the BDF contains only one bitmap size, the generated WOFF cannot reproduce the appearance of other sizes accurately. Preserve the original BDF for archival or pixel-perfect use, and retain the source project if the font will be edited later.

Check the BDF license before publishing the WOFF. Also test Unicode coverage, right-to-left text, combining marks, kerning, baseline metrics, and fallback behavior; a successful file conversion does not guarantee correct text shaping.