DTL OTMaster

DTL OTMaster is a technical OpenType font editor developed by Dutch Type Library and URW Type Foundry. With OTMaster, you can inspect, troubleshoot and modify OpenType and TrueType fonts in a non-invasive way — in all their flavors, including variable fonts, color fonts, TTC collections, WOFF2 web fonts and CID-keyed OTF fonts.

With OTMaster’s Glyph Editor, you can import a monochrome EPS or SVG drawing, ornament or logo, and add it as a new glyph or replace an existing glyph in a font.

The new version 7.9 lets you test OpenType Font Variations, view and change OpenType Layout features, edit low-level OpenType font tables, and fix bugs or problems.

When you open an OTF or TTF file in FontLab VI or Fontographer, the font is converted into an internal format. You can then perform large and small modifications. When you export the font, the font is completely rebuilt, so some of the original data may be modified, updated or discarded.

OTMaster is different: it does not perform any conversion but lets you examine the internal structures of the binary font, and perform small targeted modifications of some portions of the font without even touching the other parts.

OTMaster is a perfect companion app for FontLab’s own font editors such as FontLab VI or Fontographer: draw, space, kern & hint in a FontLab editor, test & tweak in OTMaster.

OpenType font tables

View and edit the inner structure of any OpenType font.
Compare font tables from multiple fonts.

Inspect and edit OpenType font tables in OTMaster
Nested Tables view and Table Comparator in OTMaster

Each OpenType font file consists of a collection of tables — binary data structures identified by four-character names such as head, name, GSUB, GPOS, or glyf. OTMaster reveals the contents of any OpenType font table in a Nested Tables view or in a Text Dump view.

Open any OTF, TTF or TTC font file, or import a WOFF2 or WOFF file, then navigate and examine the contents of any OpenType font in OTMaster. Refer to the OpenType and TrueType specifications for detailed explanation about each font table — it’s an excellent way to learn the structure of the OpenType fonts, and to become familiar with how fonts work.

In the Nested Tables view, you can edit most fields inside the font tables. You can also view and export the contents of each font table as a plain-text or XML file. Use the Table Comparator to check and edit various OpenType table fields across many fonts.

Troubleshoot, proof, fix & tweak

Check the font’s language coverage.
Detect and fix common font problems. Tweak font details.
Print text specimens, glyph drawings or character maps.

Troubleshoot, proof and fix font families in OTMaster
Proofing Tool and Consistency Checker in OTMaster

Use Consistency Checker to check which scripts and languages your font covers, and to automatically detect and correct family-linking, linespacing (vertical metrics) or encoding (Unicode range and codepage coverage) problems.

Use the new Proofing Tool to print or export to PDF all or selected glyphs (one or multiple per page) of the current or all open fonts, or specimens with custom text. Show, hide or customize the outline, points, glyph and font metrics, labels and other details.

OpenType Font Variations

Preview and edit instances and tables in variable fonts.

Test and tweak OpenType Font Variations in OTMaster
Text Viewer, Font Variation Viewer and Side by Side Viewer in OTMaster

Font Variations is an extension of the OpenType font format that allows fonts to change their weight, width and other aspects of appearance on the fly. OTMaster 7.9 supports variable fonts in both TrueType and CFF2 flavors. You can explore the variation tables (fvar, STAT, HVAR, MVAR, avar, cvar, gvar, CFF2) and edit most of them.

Use the new Font Variation Viewer to preview a variation instance in the Text Viewer or the glyph map. Pick a predefined instance from a list or use sliders to choose an arbitrary instance. Save an arbitrary instance as a predefined instance and edit existing instances. Use the improved Side by Side Viewer to compare glyphs and predefined instances from all open fonts.

OpenType Layout features

Visually inspect & edit OpenType Layout features.
Import and export feature definitions in FEA format.

Test, edit, import and export OpenType Layout features in OTMaster
Text Viewer and GPOS/GSUB Viewer in OTMaster

OpenType fonts can include font features that substitute and precisely position glyphs. This allows for correct typographic rendering of Arabic or Indic text, for automatic small caps, swashes, ligatures, as well as stacking diacritical marks and cursive attachment. Use the Text Viewer to test your font rendering and OpenType features on longer text strings, including texts in complex scripts such as Arabic or Devanagari.

Use the GPOS/GSUB Table Viewer to perform a detailed visual analysis of all OpenType Layout substitutions in the font’s GSUB table, or to check and edit OpenType kerning and mark positioning in the GPOS table. Edit the mark positioning visually (drag the mark, Shift+drag for horizontal adjustment, Shift+Alt+drag for vertical adjustment), or use the numeric fields to edit any GPOS adjustment, including kerning. Edit legacy TrueType kerning with the kern table Viewer.

Export and import OpenType feature definitions in FEA format. When OTMaster imports feature definitions in the FEA format, it intelligently subsets them to match the font’s glyph set, so you can develop a large FEA file that defines features for many writing systems and import it into a smaller font. Import the exported FEA file into FontLab VI’s Features panel.

Add, copy, edit, import a glyph

Add, modify or copy single glyphs.
Export & import glyph outlines to and from drawing apps.

Add, copy or edit a glyph in OTMaster
Glyph Editor in OTMaster

Use OTMaster’s Glyph Editor to add or modify a glyph in an non-invasive manner: all of the font’s naming, hinting, kerning and OpenType Layout features will be intact — just as if you were using a high-precision surgical laser knife.

Export a glyph into EPS or SVG, edit it in another app and import it back into the font. This allows you to add an extra symbol such as an ornament or a logo into the font without a potentially complex process of rebuilding the font from its sources.

Use the Glyph Copy Tool to copy a glyph from one font to another. Use the Text Viewer or the Glyph Editor to edit the glyph metrics (advance widths). OTMaster’s glyph editing, spacing and copying is a good choice if you only need to change one or a few glyphs — for larger modifications, use FontLab VI.

Integrate your workflow

Use FontLab VI and OTMaster together to improve your font production.

Integrate your font development workflow with FontLab VI and OTMaster
Editing color glyphs in FontLab VI and viewing them in OTMaster

Together with FontLab VI, OTMaster forms an integrated type design and font development workflow. Draw, space, kern, hint and test your fonts or font families in FontLab VI. Export the fonts into monochrome, variable or color OpenType formats. Then use OTMaster to examine the results, produce test printouts, make last-minute modifications or produce customized font versions for individual clients.

OTMaster works with surgical precision: it will only modify the portions of the font that the developer wishes, leaving all other structures unchanged. This makes OTMaster a great companion to any font editor and an indispensable element even in the most complex OpenType font production workflow.
— Adam Twardoch, Fontlab Ltd.

OTMaster Summary

Installing on Windows
  • OTMaster 7.9 for Windows is a 32-bit app that runs on Windows 7 and newer, including Windows 10 (either the 32- or the 64-bit version).
  • To install the app: After unzipping the downloaded file, copy the DTL OTMaster 7.9 folder into your C:\Program Files folder, navigate to C:\Program Files\DTL OTMaster 7.9\Program Files, right-click otm.exe and choose Send To > Desktop (create shortcut).
  • To run the app: Double-click otm or otm.exe - Shortcut on your Desktop.
Installing on MacOS
  • OTMaster 7.9 for Mac is a 64-bit app that runs on Mac OS X 10.10 Yosemite or newer, including macOS 10.14 Mojave.
  • To install the app: Double-click the downloaded DMG. Drag DTL OTMaster 7.9.app into your /Applications folder.  
  • To run the app: When you start the app for the first time, navigate to the Applications folder, Ctrl+click DTL OTMaster 7.9.app and choose Open. Click Open. Subsequently, just double-click the app icon.
Improved in OTMaster 7.9
  • Side By Side Viewer: Print, show variation instances, only show glyphs that are non-interpolable or differ in width.
  • Table Comparator: Make tables consistent across a family, enhance, or remove entries.
  • GPOS/GSUB Table Viewer: When editing mark attachment visually, hold Shift-drag to move marks horizontally, hold Shift+Alt to move them vertically
  • OpenType tables: Support for OS/2 table version 1–5, auto-calculate new fields when upgrading table version. Show X,Y positions in glyf table comments.
  • Consistency Checker: use_typo_metrics checkbox
  • Import/Export: Export fonts to UFO format. Export instances from variable fonts to URW QQ or BE files. Export AFM with original UPM.
  • Text Viewer: Edit glyph metrics (advance width). Easier handling of texts.
  • Glyph Editor: Point List panel. Tabs moved from bottom to top. Reset to maximum Em-square. Antialiasing. Center vertically in Em square. Edit glyph metrics. Point numbering (no virtual anchor points in TT fonts). Marker Size, Fill Anchor Points in Preferences.
new in OTMaster 7.9
  • OpenType Font Variations support: New Font Variation Viewer & instances editor. Support for fvar, gvar, CFF2, STAT, HVAR, MVAR, meta tables. Show instances and isomorphic compatibility in Side by Side Viewer. Variation support in the Glyph Viewer, Text Viewer and Glyph Editor.
  • Proofing Tool: Print or export to PDF all or selected glyphs (one or multiple per page) of the current or all open fonts, or specimens with custom text. Show, hide or customize the outline, points, glyph and font metrics, labels and other details.
Font FORMATS
  • Opens OpenType CFF & CFF2 (OTF) fonts, OpenType TT / TrueType (TTF) fonts and TTC collections (TTC), also with variations (CFF2, gvar) and color tables (SVG, sbix, CBDT, COLR). Imports WOFF & WOFF2 web fonts, OpenType features (FEA). Glyph Editor imports monochrome EPS & SVG files.
  • Saves OTF & TTF files. Exports WOFF or WOFF2 web fonts, OpenType features (FEA), UFO, AFM font metrics, URW files (BE, IK, QQ etc.). Glyph Editor exports glyph outlines in EPS or SVG format.