New OpenType editor: DTL OTMaster

blokland's picture

The Dutch Type Library and URW++ Design & Development proudly present DTL OTMaster (OTM), a highly sophisticated application for reviewing, editing and saving tables of fonts with a snft file structure, as there are CFF and TTF flavored OpenType fonts, TrueType fonts and TrueType Collection fonts.

Font editors, like for instance the DTL FontMaster suite, FontLab Studio and FontForge, rely on their own internal data formats for type design and font production. From these data, binary fonts for the end-user are compiled as the last step in the font production process.
OTM is a tool for inspecting and adjusting such binary fonts, irrespective of the font editor used for their creation.

OTM makes the editing of tables possible from a graphical user interface. It comes with built-in tools like the Glyph Editor for proofing and editing contours or even drawing glyphs from scratch. A ‘kern’ Table Viewer is available for proofing and refining the kerning, and a ‘GSUB’/‘GPOS’ Viewer to visually test (and in case of GPOS also adjust) these OpenType Layout tables.

DTL OTMaster was programmed in Hamburg, Germany at URW++ Design & Development, renowned for pioneering in the field of font technology development for more than thirty years. The FM Team (Dr. Juergen Willrodt, Axel Stoltenberg, Hartmut Schwarz, Peter Rosenfeld and Frank E. Blokland) was joined by Karsten Luecke as advisor and also author of the extensive and detailed OTM manual and Nikola Djurek for the design of the function icons.

OTM is available for Mac OS X, Windows and Linux. Free Light versions are available for: Mac OS X (download), Windows (download) and Linux (download).

The downloads also contain the OTM manual in PDF format.

AzizMostafa's picture

Is it useful for Arabic fonts also?
Thanks with Flowers

blokland's picture

AzizMostafa: ‘Is it useful for Arabic fonts also?’

Please try the OTM Light version and let me know your findings.

Theunis de Jong's picture

(sulking) Oh crap. It's really a very good and thorough piece of work ...

(Background: I was just getting into manually decoding CFFs to prise out those last slivers of valuable information for my own implementation. Oh well ... at least now I have something to cross check my data against ...)

AzizMostafa's picture

Blokland, I will try my best.
Please allow 2 weeks to explore it.
Thanks one again with Flowers.

blokland's picture

Theunis de Jong: 'It’s really a very good and thorough piece of work ...'

Thanks for the compliment. This is another one (especially Dr. Juergen Willrodt deserves the credits here) by Dr. Ken Lunde, Sr. Computer Scientist at Adobe, on Thomas Phinney's blog (
'As someone who works with OpenType fonts on an every-day basis, and with the tools that are used to build and check them, I would like to state here that DTL OTMaster is a fabulous tool. The best way for me to characterize it is that it gives me the power of AFDKO’s “spot” tool, and that of TTX, but wrapped up in nice GUI. It handles CJK fonts well, including those with a large number of glyphs. I especially appreciate that there is a Mac OS X version, because that is the OS that I use.'

AzizMostafa: ‘Please allow 2 weeks to explore it.’

OTM supports mark positioning lookups and can display them. These mark to base, mark to mark and mark to ligature positions are editable in OTM. They are also supported when a features file is imported. Since OTM is based on the latest version of the Adobe SDK it supports the GPOS mark features and one can create a GPOS table from the features file.

I wrote: 'The downloads also contain the OTM manual in PDF format.' and I would like to add here that version 1.5 of the OpenType specs is attached and linked to the manual, thanks to the permission granted by Microsoft.

twardoch's picture


I have downloaded

The archive contains two files:

There is no PDF file included.

Also, when I open OTM_Light_1.0 (since I'm not running Leopard), an application called Automator opens, and that's it. No indication what should happen afterwards. Can you advise?


blank's picture

@Adam: Running OTM_Light_1.0 should start the installer; the PDF is installed along with the application. It sounds like your system is trying to open the installer VISE files with the Mac OS Automator app. I’m not sure why that would happen, but try repairing permissions and rebooting.

blokland's picture

I wrote: 'OTM is available for Mac OS X, Windows and Linux. Free Light versions are available for [...]'

To complete this information about OTM:

The full version of DTL OTMaster costs Euro 255 and can be purchased from:

twardoch's picture

Running OTM_Light_1.0_Intel_Leopard does indeed launch the installer (but OTM does not install since the OS is Tiger) but OTM_Light_1.0 launches Automator — I fail to understand why.

paragraph's picture

I tried earlier, and the first thing it asked for was the admin password. This is what it looks like on my system:

The file type associations should be the same on your system. It installed OK. It really looks quite powerful ...

blokland's picture

Adam Twardoch:
'[...] OTM_Light_1.0 launches Automator — I fail to understand why [...]'

Thanks for notifying me. Although I could not reproduce the error, I have built new VISE X installers which you can download from:

Hopefully the installer for OS 10.4 (and previous versions) functions well on your machine. Please let me know the outcome.

blokland's picture

The for some time more or less slumbering Community forum at the FM site has been re-installed and is open now for whoever wants for instance to exchange info on DTL OTMaster.

The programmers at URW++ will be monitoring too, and provide information directly, if requested.

blokland's picture

New DTL OTMaster Light versions for Mac OS X, Windows and Linux are available from the downloads page at the DTL FontTools web site.

New in DTL OTmaster (Light) version 1.0.1:
- Support for the very latest edition of the AFDKO 2.5.
- Changed export of the GDEF table.
- Bug fix for crash during export of OpenType Layout features files and Character Layout files under Mac OS 10.4.x and 10.3.x.

Very occasionally a problem was reported concerning the VISE installers for the Mac. New VISE X installers have been generated to solve this.

blokland's picture

A new version (2.0.0) of DTL OTMaster is available now.
The functionality of DTL OTMaster has been enhanced considerably in the new 2.0.0 version. For instance the Glyph Editor now supports the option to import and export EPS and SVG data. It is also possible to cut, copy and paste glyph data between CFF and TTF fonts. Imported glyphs can be autohinted.
The OpenType Layout features processing is based on latest build of the AFDKO 2.5 version and the OpenType specification 1.6 is supported. The Concistency Checker has been enhanced with new ‘Version’ and ‘Statistics’ options.
Especially because of the new glyph editing functionality and the option to add EPS and SVG data to OpenType (CFF and TTF) fonts, DTL OTMaster 2.0.0 is not only suitable for professional font producers, but also for graphic designers who want to add special characters and logo’s to existing fonts (if the end user license that came with the font in question permits this, of course).
• Download DTL OTMaster Light 2.0.0
New in version 2.0.0:
— Support of the latest ‘build’ of the AFDKO version 2.5.
— Support for OT Specification V1.6.
— Support for Mark Filtering Sets
— Support for cv00–cv99, ss01–ss20
— Support for feature name tags
— Two new options in the Consistency checker:
1. Version checker,
2. Glyf and Header entries checker.
Glyph Copy Tool supports copying OTF(CFF) <–> TTF now.
— Cut/Copy/Paste between Bezier outlines (CFF) and quadratic splines (Glyf).
— EPS import & export
— SVG import & export
— Metrics editing and update (hmtx, vmtx) in the glyph editor.
— Autohinting (for single glyphs).
— Display of hints for CFF Fonts.

Tim Ahrens's picture

I just tried installing the new Light version but it still says it is OTM Light 1.000.

Is there any way how I can find out which version I am actually using? The program does not seem to have an "About" function.

Joshua_Koomen's picture

Try to find a Read Me file inside the folder of the software.

I dont have OTM, but DTL LetterModeller has its own Read Me file inside the software folder. I guess the programmer would do the same with OTM.

k.l.'s picture

Hi Tim, the status bar at the bottom of th window should show the version/date. If this notice is gone already, it should still be in the File - Messages dialog, at the very top.

blokland's picture

Tim: '[...] the new Light version but it still says it is OTM Light 1.000 [...]'

Yes, that is correct... or actually it is not. We fixed this in the full edition some time ago (and now we will do this in the Light version too). Yoshua is right about the Read Me file, this should confirm that what you have downloaded is actually version 2.0. Sorry for this.

svenni's picture

Just downloaded and installed it. Tried opening an OT font, the program told me that it is not able to save. If this version doesn't have save capabilities, isn't "Light" a misnomer? Shouldn't it be called "Demo"?


blokland's picture

Sveinbjörn: [...] Shouldn't it be called "Demo"?

Basically this depends on how much one appreciates the checking functions OTM Light offers (see also: and options like for instance the export of features files. It is the only tool of its kind, which offers a GUI anyway, and I reckon that there are quite some OTM Light versions in use in combination with other font tools.

And labelled either ‘Demo’ or ‘Light’, it is for free, isn’t it?

John Hudson's picture

Svenni, look at it this way: the light version of OTM is a diagnostic tool, the full version lets you do surgery. I value having the full version because I sometimes need to perform post-production operations on font data, because in my workflow a TTF or OTF becomes the source format for OTL and hinting work. But if one has a workflow in which a program like FontLab remains the source format throughout, up to the point of final font generation, then OTM is useful as a means of examining generated fonts, quality assurance, etc. and you only need the light version.

twardoch's picture

Indeed, I consider OTMaster Light a very powerful "in-depth font viewer". For example, its Tools/'GPOS'/'GSUB' Table Viewer is a quite powerful and useful tool to examine the functionality of the compiled OpenType Layout tables.

TypeSupply FeatureProof [1] offers a similar functionality, but OTMaster is much more robust with more complicated fonts (e.g. complex-script fonts for Indic languages, which FeatureProof simply does not open at all). Also, OTMaster works on both Mac OS X and Windows, while FeatureProof is Mac-only. On the other hand, FeatureProof offers a more practical interface for testing contextual OpenType Layout features in a "real text string".

And yes, indeed, the full version of OTMaster allows you to edit pretty much any aspect of the low-level structures of a TrueType or OpenType font. TTX/FontTools [2] allows pretty much the same, but in a rather different manner: OTMaster offers a graphical user interface while TTX/FontTools allows the user to convert an entire TTF or OTF font (or one selected table) into XML, edit the XML in a text editor, and convert it back into a font. Also, installing and setting up TTX/FontTools can be challenging for some users, while OTMaster works "out of the box".

Both working manners have their advantages. If you need to make more changes, the XML workflow (through TTX/FontTools) can be more efficient, but for a simple fix or two in a font, OTMaster is the better solution.

I definitely think DTL OTMaster is an excellent product.



Arno Enslin's picture

@ Adam

Also, installing and setting up TTX/FontTools can be challenging for some users, while OTMaster works "out of the box".

Mainly because the installation instructions are out of date and incomplete and mainly because some developers seem to develop for themselves only:

I mean, it is wasted time, if each of some users has to solve the same problems instead of having no problems because of updated instructions.

twardoch's picture


please consider that opensource efforts such as TTX/FontTools are made by volunteers in their spare time. The concept of opensource is that any developer can, and is encouraged, to contribute. The software comes free of charge, as is. There is nobody who collects license fees, and there is nobody who gets paid for their work on the software.

When I produced the build instructions for TTX/FontTools for Windows five or so years ago, I worked on Windows. More than two years ago, I completely switched to Mac OS X, and can no longer maintain build instructions for Windows.

Anyone willing to contribute updated build instructions for TTX/FontTools for Windows is welcome to do so (or is welcome to find a Python for Windows developer who is willing to do it, and pay him). This is the key concept of opensource.

Milton Friedman used to say "There is no such thing as a free lunch". If the lunch is said to be free, it may mean that you need to participate in cooking it.


twardoch's picture

This might be of interest: DTL OTMaster 2.3 is now available on

Richard Fink's picture

I just bought 2.0 not thirty days ago. There upgrade is free, I assume?

blokland's picture

Richard: There upgrade is free, I assume?
Yes, the upgrade is free for OTM 2.0 users; you will receive download info for version 2.3 shortly.
New in version 2.3.0
— Support for the display of cursive attachment (Arabic).
— Enhanced display of mark-to-base and mark-to-mark attachment points.
— Interactive editing of mark attachment points.
— Export of kerning-data as AFM file (only from ‘kern’ table).
— Two new options in the Consistency checker:
1. Unicode ranges,
2. Codepage ranges.

Richard Fink's picture




blokland's picture

New: DTL OTMaster 2.4
A new version of OTM has become available. The new functionality comprises improved export of OpenType layout features, a couple of enhancements in the OTF Consistency Checker and the options to change the table version numbers in the ‘post’ and ‘gasp’ headers.

DTL OTMaster can be used to export OpenType layout tables present in a font. The exported OpenType layout features files can be read-in directly without any alterations. And although the way the exported features are listed could be different (due to the inevitable interpretation of the binary tables) from the features-description that was used for generating the font originally, the functionality should be completely identical.
OTM 2.4 supports the latest AFDKO 2.5 build and can be used to update the OpenType layout features in a font. Any OpenType layout features file with the AFDKO syntax can be imported, even if the listed features are not covered by the font’s character set. The modified Hatch OpenType (‘HOT’) tool will remove the none-covered features during font generation. Of course, to make all applicable features work, the character naming convention should be identical in both the font and the OpenType layout features file.

The OTF Consistency Checker in OTM 2.4 contains a new, extensive, ‘Language’ section, which can be used to list and print the (missing) glyphs that a font supports for a specific language.

dezcom's picture

Thanks, Frank,

Is this a free upgrade for previous version owners?

blokland's picture

Chris: Is this a free upgrade for previous version owners?
Yes, it is for OTM 2.x owners and they will be informed shortly.

dezcom's picture

Thanks, I'll look for it to arrive.

Richard Fink's picture

>The OTF Consistency Checker in OTM 2.4 contains a new, extensive, ‘Language’ section, which can be used to list and print the (missing) glyphs that a font supports for a specific language.

Downloaded the upgrade today. This is a great feature.

Tim Ahrens's picture

Sounds interesting!

Is there any trial version for OTMaster 2.4? On the website I could only find OTMaster Light 2.0.0.

twardoch's picture

I can also attest that the AFDKO functionality of DTL OTMaster 2.4 is great.

1. The export of AFDKO feature definition files from existing OpenType fonts has been improved so now OTMaster can export the code in such a way that AFDKO 2.5-compatible compilers such as MakeOTF, Fontographer 5 or the upcoming FontLab Studio 5.1 can easily compile it, problem-free.

2. The intelligent subsetting of the AFDKO code works very well. If your glyph naming is consistent, you can use one large AFDKO file that covers the largest possible glyph set. You can import it into any font that uses the same glyph names, and OTMaster will only add the feature definitions that are covered by the glyph set.

An example on how this can be used:

Open a large multi-script OpenType font in OTMaster, export the AFDKO code, open the same OpenType font in a font editor such as Fontographer or FontLab Studio or even TypeTool, remove some glyphs, generate the font, open it in OTMaster and import the previously exported AFDKO code. The rules or lookups that no longer apply to the font (because the relevant glyphs are no longer present) will be transparently ignored, and only features that are covered will be included.

In fact, you can then export the AFDKO file again from that font, and then you'll get the subsetted AFDKO file. So rather than removing lines of code by hand, editing your classes etc., you just use OTMaster as a "filter" that will process your code. You can then, perhaps, make some small changes to that new, subsetted AFDKO file, and take it into any tool such as FontLab Studio, Fontographer or MakeOTF.

Of course this means that you can have a large "master" AFDKO feature definition file, and use OTMaster to add the code to any font you're making, regardless of the actual glyph set. You can either import the AFDKO file in OTMaster and then save the new OpenType font (with features included) right from OTMaster, or -- if you want ultimate control -- import the master AFDKO file into the font in OTMaster and then export it again: then you'll get the custom-tailored AFDKO file, and you can perform some additional manual edits (e.g. if you have some special "calt" or "ssXX" features which are not present in your master file).

This is, potentially, a huge time-saver for people making OpenType fonts.

Last year, I've started using OTMaster as the final step of font production, after generating the font from Fontographer or FontLab Studio. OTMaster gives you a low-level OpenType-spec-native view at the font, quite like FontTools/TTX, but wrapped in a quite clean user interface.

OTMaster is a great "illustrator" for the OpenType spec. If you want to take the step of reading through the OpenType spec at some point (which I do recommend if you are developing fonts), reading the spec is much more pleasant if you open a font in OTMaster and view the actual tables organization and values. This will help you understand the spec much better. I hope for many of you, if you do this, it'll allow your brain to make "click" at some point, and you'll quite likely be able to finally "get" the inside structure of OpenType font. IMO, that's tremendously helpful.

The trial version of version 2.4 is not available. OTMaster Light 2.0 is the latest trial version available. As a trial, it works quite well. You can familiarize yourself with the tool and see whether it's any good for you, in general. Also, there's a small video that I've created showing DTL OTMaster in action. The video is based on OTMaster 2.3, so some of the new features are not shown.

DTL OTMaster 2.4 will be available shortly at


dezcom's picture

I just loaded it! Love all the new additions! Thanks, Frank!

twardoch's picture

DTL OTMaster 2.4 is now available on, along with Fontographer 5.1!

During this summer, a Fontographer 5.1 + DTL OTMaster 2.4 bundle is available at US$449.00. We at Fontlab Ltd. are very exciting about this collaboration with Dutch Type Library and URW++.

A list of new features for both Fontographer 5.1 and DTL OTMaster 2.4, along with free updates for users who purchased the tools on is also available.

The Mac OS X versions of Fontographer 5.1 and DTL OTMaster 2.4 are compatible with Mac OS X 10.4 and higher, including 10.7 Lion. The Windows versions are compatible with Windows XP, Vista and 7. You may want to review the note about compatibility of other FontLab products with Mac OS X 10.7 Lion.

Adam Twardoch
Fontlab Ltd.

blokland's picture

Adam: ‘[…] OTMaster can export the code in such a way that AFDKO 2.5-compatible compilers such as MakeOTF, Fontographer 5 or the upcoming FontLab Studio 5.1 can easily compile it […]
Probably most of you have noticed already that the ATypI conference program for Thursday 15 September 2011 has been slightly changed. At 11.50 hrs. Adam will give a talk titled OpenType Mastering. The following paragraph is an excerpt from the synopsis:
Fontographer is a bit like the guitar or piano of a type designer – it focuses on the creative aspects of making fonts. FontLab Studio offers creative tools and a fair bit of engineering gear. But DTL OTMaster is a true font engineering tool that allows you to control the final quality of your digital font files. In this talk, Adam will show how these three applications can play hand in hand.

blokland's picture

Currently the production of a new edition of DTL OTMaster is finalized. OTM 3 will be presented at the ATypI Amsterdam conference October 2013. A number of new functions will become available:

1. Export IK/II/BE/IB
2. Export All (IK/II/BE/IB, UFM, CHA, FEA)
3. Import/Export IVS
4. Improvements for the Glyph Editor:
– Background display: Match Unicode
– Many new editing options
5. Switch for Subroutinization in CFF
6. Support OS/2 Table V… (a secret still ;-)
7. Side-by-Side Viewer (multiple Fonts)
8. Change table view with ( + )
9. Edit Feature Parameters
10. Consistency Checker:
– Check Names has been modified

Besides the full version, there will be a new Light edition (for €49.50), from which the import/export functionality (including the OpenType Layout features subsetting) and glyph-editing functionality is removed.


John Hudson's picture

Frank, any chance of rolling support for the new COLR and CPAL tables into this version? The spec is available from MS now, and it would be great to have a tool to view and edit these tables. A colour picker for the CPAL table would be really nice, but even just editable RGBA values would be welcome.

blokland's picture

Hello John,

Karsten, who is currently working on the manual, also came up with this question. I followed the discussion on the OT-list, and will talk about the support for the new COLR and CPAL tables with Juergen. Hopefully he, Axel and Hartmut will find some time to do this before ATypI Amsterdam.


blokland's picture

Stop the Presses

OTM 3 will have support for the new CPAL color tables and the recently published SVG stuff too.


dezcom's picture

"Karsten, who is currently working on the manual"

Wonderful! He will do an excellent job and a manual is definitely needed.

blokland's picture

Chris: ‘He will do an excellent job and a manual is definitely needed.

Karsten already did a wonderful job when he wrote the former OTM manual. The concise addendum for version 2.4 was made by me.


dezcom's picture

This is my first knowledge that either existed, sorry.

Thomas Phinney's picture

OTM is a really nice tool. One of my two indispensable font-spelunking tools (along with TTX/FontTools).

I look forward to seeing the new v3!

Theunis de Jong's picture

"Stop the colour Presses" 😄

Every now and then innovations in font design didn't percolate into actual design software because there were no fonts to use them with, and there were no fonts because the software wasn't there. And the software wasn't there because there was no demand from the design software writers ...

It's fantastic that OTM so quickly integrated this, as did FontCreator and Type Light! Now it's up to the higher echelons of software vendors to implement proper support, first for viewing, then for printing.

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