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DTL OTMaster


DTL OTMaster 3.7

Examine and Fix OpenType Fonts. For Mac and Windows.

The technical OpenType editor

An affordable font utility that allows users to visually edit the contents of tables in TrueType and OpenType fonts.

DTL OTMaster (OTM) is a highly sophisticated application for reviewing, editing and altering tables and contours of OpenType fonts (.otf and .ttf), TrueType fonts (.ttf) and TrueType Collection (.ttc) fonts, including CID-keyed OpenType fonts, CJK (Chinese, Korean, Japanese) and complex-scripts (Indic, Arabic etc.) fonts.

Version 3.7 improvements

Working with multiple fonts

  • NEW! Compare glyphs across all open fonts with the new Side by Side Viewer tool
  • NEW! Easily compare and edit font parameters across all open fonts with the new Table Comparator tool (tables: head, hhea, vhea, OS/2, maxp, post header, CFF top dict, PCLT)
  • IMPROVED! Easily jump to the same table location across all open fonts with the Next File Above and Next File Below keyboard shortcuts

Updated font format support

  • NEW! View and edit the new Microsoft color font format (COLR+CPAL tables) with the new Color Viewer tool
  • NEW! Edit the optical size range parameter in OS/2 table version 5
  • NEW! Import/export Ideographic Variation Sequences (IVS) for CJK fonts
  • NEW! Export URW++ font formats
  • IMPROVED! Detect name table problems in the improved Consistency Checker tool
  • NEW! Enable/disable subroutinization of the CFF table in Preferences

Revamped Glyph Editor tool

  • NEW! Detect and automatically fix glyph outline problems with the new Inflections and Flat Curves highlighting and the new Improve tool
  • NEW! Reverse overlap removal with the new Disconnector tools (X and I)
  • NEW! New Measure, Grid, Guidelines tools
  • NEW! Glyph clipboard library
  • IMPROVED! Enhanced background layer handling

To upgrade to DTL OTMaster 3.7 from older versions (EUR 50), e-mail us at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it


DTL OTMaster: glyph viewer DTL OTMaster: GSUB/GPOS viewer, GSUB table, Image view
Click on a thumbnail to see the full screenshot. See more screenshots...


Introduction to DTL OTMaster on Vimeo
Click on the thumbnail to see a short video introducing DTL OTMaster or open it on Vimeo.


DTL OTMaster reveals the secrets of your OpenType and TrueType fonts without your having to slog through text dumps or binary code. It makes the editing of tables easy and smooth using its graphical user interface.

Furthermore, it comes with a built-in Glyph Editor for proofing and editing contours or even drawing glyphs from scratch. The kern Table Viewer provides a kerning class editor for proofing and refining the kerning, and the GSUB/GPOS Table Viewer lets you visually test (and in case of GPOS also adjust) these OpenType Layout tables.

One of the most remarkable functions in OTM, is the option to import and export OpenType Layout features files. During import OTM compiles the OpenType Layout features with the AFDKO (Adobe Font Development Kit for OpenType) syntax (.fea) and produces binary OpenType Layout tables.

DTL OTMaster - the technical OpenType editor. A perfect font tool for professional font users, type designers, as well as software vendors and developers.

DTL OTMaster: Overview
Click above to see a screenshot of DTL OTMaster.

In-depth, non-invasive

Examine, report, print

Why does your Euro character keep turning up in the wrong place like a tuxedo at a Halloween party? Maybe he got lost because of a lousy cmap? Check it out with OTM's table viewer and get him to the wedding on time.

DTL OTMaster (OTM) is an excellent tool for looking deep into an OpenType font?s hidden treasures. More...

Add, copy or edit a glyph

Your client's specified font has an ampersand that looks like pig's entrails. No need to haul out the meat cleaver big font editor. A little judicious surgery with OTM's glyph editor can solve the problem in minutes.

When the font you?re using is missing a glyph or an existing glyph has an inappropriate shape, OTM allows you to fix this without breaking or changing the font?s original hinting, kerning, or OpenType Layout features. More...

Test and edit OpenType Layout features

If you've cooked up or discovered a recipe for a great feature set you don't want it to disappear after you've served it up just once. Keep the formula around for future font feasts by exporting a .fea file from OTM.

Swashes, small caps, marks, cursive attachment - what's going on?  More...

Fix families, linespacing, encoding

Your pretty swash font looks like it got a buzzcut: the tall glyphs are all clipped at the top. Like a bad part the linespacing is different on Mac and Windows? Or you wanted an Afro but the font appears in the font section for Greek fonts, although it includes only two Greek letters? The Light style appears after the Regular style in the font menu, or does not appear at all? More...

Last-minute adjustments

Your OpenType font is perfect, but... Oops, you've forgotten to update the version string. Or there's an OpenType glyph that you'd like to access directly from the keyboard. Or the font's underline is too thin. Or the font's antialiasing is not quite like you'd like it to be. OTM lets you perform last-minute changes without you needing to rebuild the font from sources - great, especially if you have a complex production workflow. More...

Is it the font? Is it the app?

If you're a software developer or vendor, DTL OTMaster will allow you to examine fonts and identify whether the problem is caused by a buggy font, or by buggy software. Developed with globalization and internationalization in mind, OTM provides deep insight into the state-of-the art Unicode-based OpenType / ISO/IEC 14496-22 font technology.

Examine, report, print

Learn how the OpenType font format works by viewing the inner structure of any OpenType font; export the contents of each font table as a plain-text or XML file; or print detailed glyph drawings or character maps. Each OpenType font file consists of a collection of so-called ?tables? ? binary chunks of data identified by four-character names such as head, gasp, name, kern, GSUB, GPOS, glyf or CFF .

DTL OTMaster reveals the contents of any OpenType font table in a friendly ?nested tree? view or in a comprehensive ?text dump? mode.

OTM comes bundled with the OpenType font format specification (in the Documentation/OTM Manual resources folder inside the application?s folder), so you can open a web browser side-by-side with OTM, and read the explanations for each table and all of its fields. It?s an excellent way to learn the structure of the OpenType fonts and become familiar with how the fonts work.

In the nested tree mode, you can easily edit most of the font table?s fields. You cand also view and export the contents of each font table as a plain-text or XML file, or print detailed glyph showings or character maps.

DTL OTMaster: 'glyf' table, Nested Tables view DTL OTMaster: 'name' table, Nested Tables view DTL OTMaster: 'OS/2' table, Nested Tables view DTL OTMaster: 'cmap' table, Nested Tables view DTL OTMaster: 'head' table, Text Dump view DTL OTMaster: 'gasp' table, Nested Tables view DTL OTMaster: 'gasp' table, Text Dump view DTL OTMaster: 'gasp' table, XML view

Add, copy or edit a glyph

OTM is a perfect tool in situations when the font you?re using is missing a glyph or an existing glyph has an inappropriate shape. You could accomplish this in any font editor, but OTM will perform the changes 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. This works even for CJK fonts and complex-script fonts such as Arabic or Indic!

With OTM?s Glyph Editor, you can add new glyphs to your font (Edit / New) or change existing glyphs using the built-in editing tools. You can even export the glyph into EPS or SVG, edit it in your favorite outline editing application (such as Adobe Illustrator), and import it back into the font (File / Import and File / Export). This allows you to add any symbols you want ? not just letters, but also dingbats, personal signatures or company logos!

After you?ve modified the glyph shape or have created a new glyph, adjust its advance width to match your preferred spacing. Also, remember to turn on Hints, choose Transformation / Character Hinting and enable Autohinting. This will ensure that your modified glyph will look good on screen. Once you finished editing the glyph, close the Glyph Editor and click on the Discard Undo Information button.

If you?ve added a new glyph to the font, you may need to adjust its name and Unicode codepoint (so the glyph becomes accessible in applications that use the font). Open the Font Viewer, find the new glyph and double-click on it. This will open the Glyph Viewer, in which you can change the name and assign the Unicode codepoint. Remember to enter the same Unicode codepoint (e.g. 0x20ac if you added a ? sign) in both Unicode and Microsoft; Unicode BMP only fields.

With the Glyph Copy Tool, you can copy a glyph (for example a special symbol or ornament) from one font to another. This will copy not only the glyph?s outline, but also its metrics, hints, and Unicode information.

DTL OTMaster: glyph viewer DTL OTMaster: glyph viewer DTL OTMaster: glyph editor DTL OTMaster: copy glyphs

Test and edit OpenType Layout features

One area where DTL OTMaster really shines is the ability to test and edit OpenType Layout features. The GSUB/GPOS Viewer tool allows you to visually check the GSUB replacements, and to test and edit kerning and GPOS positioning. You can also export feature definitions in AFDKO 2.5 format for later re-use.

One of the exciting aspects of OpenType is the powerful OpenType Layout mechanism. Rather than having a 1:1 relationship of glyphs and characters, and a plain kerning table, OpenType fonts allow for glyphs to be substituted, as well as precisely positioned (both horizontally and vertically). This can even be done contextually, i.e. only when a glyph is surrounded by specific other glyphs. Thanks to this, OpenType fonts can be ?smart?, and include automatically inserted small caps, swashes, ligatures, stacking diacritical marks, or cursive attachment.

DTL OTMaster includes the GSUB/GPOS Viewer, a specialized module that allows you to visually check all of the font?s GSUB replacement commands and GPOS positioning rules. Some of the GPOS features such as kern or mark can be edited visually (along with the old-style TrueType kern table, in the kern Table Viewer).

All of the font?s features can also be exported into .fea feature definition files that use the state-of-the-art Adobe FDK for OpenType (AFDKO) syntax, version 2.5. You can edit those files in a plain-text editor, and import them back into the original font ? or into a different font, even if the font has a different character set. You can also use the feature definition files with FontLab Fontographer 5, which may save you a lot of time-consuming hand-coding.

DTL OTMaster: GSUB/GPOS viewer, GSUB table, Data view DTL OTMaster: GSUB/GPOS viewer, GSUB table, Report view DTL OTMaster: 'kern' table viewer DTL OTMaster: GSUB/GPOS viewer, GPOS table, 'kern' feature DTL OTMaster: GSUB/GPOS viewer, GPOS table, 'mark' feature DTL OTMaster: GSUB/GPOS viewer, GPOS table, 'mark' feature DTL OTMaster: GSUB/GPOS viewer, GPOS table, 'curs' feature

Fix families, linespacing, encoding

OTM?s Consistency Checker can automatically detect and correct family-linking, linespacing (vertical metrics) or encoding (Unicode range and codepage coverage) problems.

DTL OTMaster: Consistency checker DTL OTMaster: Consistency checker DTL OTMaster: Consistency checker DTL OTMaster: Consistency checker

Last-minute adjustments

The font looks too thin on the screen because of antialiasing, and you?d like to turn it off (in the gasp table)? Your favorite glyph is not accessible in your favorite application, so you need to add a PUA Unicode codepoint (in the cmap table or the glyph viewer)? The automatic underlining is too thin (the yStrikeout fields in the OS/2 table)? The sanserif font is a bit ?too large on the body? compared to companion serif typeface (the unitsPerEm field in the head table)? OTMaster?s table-editing interface can help you fix all these problems without having to rebuild the font from sources ? which might be a problem, especially for Chinese, Japanese, Korean, Hebrew, Arabic or Indic fonts.