A solution for Windows Font Viewer 'is not a valid font' error

Shahab Siavash

Hi,

I've been hearing about this for more than a year now. Some of the users have been telling me that they had received this error before. But I personally never had a problem, until I did search for it and found a lot of users complaining about this. It is a valid font, you install it, no problem, another user with the same OS like Windows 10 tries to install the font and get this error. It never goes away and also doesn't seem to be based on anything. Sometimes it's ttf files, sometimes otf and sometimes totally random. 
The tech guys all over the internet finally concluded that it may be related to Windows Firewall! No one knows why and how! But my question is is there any font programmer here that could help me to understand why is this happening and how to fix it? I don't know what should I say to my customers sometimes, they have paid for the fonts. Fonts are working and had been tested, but somehow this happens!

Thanks!

Adam Jagosz

I've been getting this error before, and I wondered if it was due to something weird in my export config. Sometimes it seemed to have happened when trying to replace an already installed font (Thomas Phinney is right here that the best policy is to uninstall the old version first, otherwise Windows does some magic with the files, it leaves the old file in the directory and copies the new file with changed name, and sometimes puts some weird locks on the files). I think the Firewall clue is probable though, because Windows. I'm curious to know more about the reasons behind this message and ways to avoid it.

Shahab Siavash

Adam Jagosz said:

I've been getting this error before, and I wondered if it was due to something weird in my export config. Sometimes it seemed to have happened when trying to replace an already installed font (Thomas Phinney is right here that the best policy is to uninstall the old version first, otherwise Windows does some magic with the files, it leaves the old file in the directory and copies the new file with changed name, and sometimes puts some weird locks on the files). I think the Firewall clue is probable though, because Windows. I'm curious to know more about the reasons behind this message and ways to avoid it.

Thanks Adam. Actually I'm also looking forward to read some good comments here.

Jeff Kellem

At least for Windows 7, it refuses to consider an OpenType CFF font valid during installation when the font Family Name is longer than 29 characters.

Though, both of those possible (guessed) names, e.g., "DejaVu Sans Mono Bold Oblique", should just be within limits. The example I gave is exactly 29 characters.

Shahab Siavash

Jeff Kellem said:

At least for Windows 7, it refuses to consider an OpenType CFF font valid during installation when the font Family Name is longer than 29 characters.

Though, both of those possible (guessed) names, e.g., "DejaVu Sans Mono Bold Oblique", should just be within limits. The example I gave is exactly 29 characters.

Thanks. I didn't know that!
Is it possible that we can find out how Windows Font Viewer actually "consider" a file a valid font? (beside the file name length) 

Thomas Phinney

I am confused about something. Under what circumstances would “Bold Oblique” be part of the Family Name? Seems like that would be the style name, unless you are one of those folks who makes every style its own windows family, not even style-linking the italics. That is a bit extreme for my taste.

Viktor Rubenko

Jeff Kellem said:

At least for Windows 7, it refuses to consider an OpenType CFF font valid during installation when the font Family Name is longer than 29 characters.

Though, both of those possible (guessed) names, e.g., "DejaVu Sans Mono Bold Oblique", should just be within limits. The example I gave is exactly 29 characters.

Win + Mac:
Family Name <= 31
PS Font Name <= 29
FOND Name <= 30

Erwin Denissen

I'm only guessing, but maybe Windows font viewer needs Internet access in order to setup digital signature verification for fonts.

From my experience you won't have this issue if you use an external font manager. Our font manager (MainType) comes with a free edition, so do give it a try.

Shahab Siavash

Erwin Denissen said:

I'm only guessing, but maybe Windows font viewer needs Internet access in order to setup digital signature verification for fonts.

From my experience you won't have this issue if you use an external font manager. Our font manager (MainType) comes with a free edition, so do give it a try.

I don't think it's related to internet access, but thanks for the application link. I remember having this before and also FontCreator install font doesn't have this problem. It makes me more curious that how and why this bug happens!

Sami Artur Mandelbaum

I had a similar problem and it was the cmap table.

AbrahamLee

@Peter Constable, can you give any insights into what validation checks Windows does to throw these errors?

Shahab Siavash

Sami Artur Mandelbaum said:

I had a similar problem and it was the cmap table.

The thing is I'm actually certain that this is not a font-related problem, because in many many cases it happens with the same font on similar operating systems (like Windows 10) and leads to different results. Sometimes you don't get any error for the exact same font file and sometimes you do!

Sami Artur Mandelbaum

Shahab Siavash said:

Sami Artur Mandelbaum said:

I had a similar problem and it was the cmap table.

The thing is I'm actually certain that this is not a font-related problem, because in many many cases it happens with the same font on similar operating systems (like Windows 10) and leads to different results. Sometimes you don't get any error for the exact same font file and sometimes you do!

Maybe is a font cache problem.
Have You tried to delet the windows font cache?

Shahab Siavash

Sami Artur Mandelbaum said:

Shahab Siavash said:

Sami Artur Mandelbaum said:

I had a similar problem and it was the cmap table.

The thing is I'm actually certain that this is not a font-related problem, because in many many cases it happens with the same font on similar operating systems (like Windows 10) and leads to different results. Sometimes you don't get any error for the exact same font file and sometimes you do!

Maybe is a font cache problem.
Have You tried to delete the windows font cache?

It is a very common bug, at least when you seach for it on the internet, so nah, it's not going to go away with - I think - anything a user would do.

Kent Lew

If it’s not something that would go away “with anything a user would do”, but it’s also “not a font-related problem” — then, I’m not sure what you’re hoping for.

Shahab Siavash

Kent Lew said:

If it’s not something that would go away “with anything a user would do”, but it’s also “not a font-related problem” — then, I’m not sure what you’re hoping for.

It's something - maybe a bug - or a built-in thing in Windows which "recognize" a file as a font and if it determines the file is not "valid", then Windows Font Viewer would not open the font. (The same file would have not any problem with another font installer on the same PC)
The reason I'm saying is not font-related because it happens to very very well-known fonts which millions of people already installed them, and the reason I'm saying it's not going away because it's connected to how Windows identifies fonts, and you won't see it on other operating systems (as far as I know).
What I - was - am looking for is to find out how Windows Font Viewer does this "recognition" which ends to this error. I hope I was clear

Belleve Invis

Shahab Siavash said:

Kent Lew said:

If it’s not something that would go away “with anything a user would do”, but it’s also “not a font-related problem” — then, I’m not sure what you’re hoping for.

It's something - maybe a bug - or a built-in thing in Windows which "recognize" a file as a font and if it determines the file is not "valid", then Windows Font Viewer would not open the font. (The same file would have not any problem with another font installer on the same PC)
The reason I'm saying is not font-related because it happens to very very well-known fonts which millions of people already installed them, and the reason I'm saying it's not going away because it's connected to how Windows identifies fonts, and you won't see it on other operating systems (as far as I know).
What I - was - am looking for is to find out how Windows Font Viewer does this "recognition" which ends to this error. I hope I was clear

To get the real reason that why GDI rejects a font you need kernel debugging.
You can try to run your font through OTS first and see whether OTS throws an error. It's very helpful for validating fonts.

Shahab Siavash

Belleve Invis said:

Shahab Siavash said:

Kent Lew said:

If it’s not something that would go away “with anything a user would do”, but it’s also “not a font-related problem” — then, I’m not sure what you’re hoping for.

It's something - maybe a bug - or a built-in thing in Windows which "recognize" a file as a font and if it determines the file is not "valid", then Windows Font Viewer would not open the font. (The same file would have not any problem with another font installer on the same PC)
The reason I'm saying is not font-related because it happens to very very well-known fonts which millions of people already installed them, and the reason I'm saying it's not going away because it's connected to how Windows identifies fonts, and you won't see it on other operating systems (as far as I know).
What I - was - am looking for is to find out how Windows Font Viewer does this "recognition" which ends to this error. I hope I was clear

To get the real reason that why GDI rejects a font you need kernel debugging.
You can try to run your font through OTS first and see whether OTS throws an error. It's very helpful for validating fonts.

Thanks, I will keep this in mind and do that for sure, but yet again it's not about my font or my experience solely, when you search "not a valid font in Windows" you get 122,000,000 results. There are pages on Font.com and Fontsmith,... about this error, so again I don't think it is a font-related problem.
My point from the beginning was to find out what's the issue with Windows Font Viewer. Obviously I couldn't make it clear enough. 

Belleve Invis

Shahab Siavash said:

Belleve Invis said:

Shahab Siavash said:

Kent Lew said:

If it’s not something that would go away “with anything a user would do”, but it’s also “not a font-related problem” — then, I’m not sure what you’re hoping for.

It's something - maybe a bug - or a built-in thing in Windows which "recognize" a file as a font and if it determines the file is not "valid", then Windows Font Viewer would not open the font. (The same file would have not any problem with another font installer on the same PC)
The reason I'm saying is not font-related because it happens to very very well-known fonts which millions of people already installed them, and the reason I'm saying it's not going away because it's connected to how Windows identifies fonts, and you won't see it on other operating systems (as far as I know).
What I - was - am looking for is to find out how Windows Font Viewer does this "recognition" which ends to this error. I hope I was clear

To get the real reason that why GDI rejects a font you need kernel debugging.
You can try to run your font through OTS first and see whether OTS throws an error. It's very helpful for validating fonts.

Thanks, I will keep this in mind and do that for sure, but yet again it's not about my font or my experience solely, when you search "not a valid font in Windows" you get 122,000,000 results. There are pages on Font.com and Fontsmith,... about this error, so again I don't think it is a font-related problem.
My point from the beginning was to find out what's the issue with Windows Font Viewer. Obviously I couldn't make it clear enough. 

To be clear: Windows Font Viewer rejects a font only when GDI rejects it.
Current GDI error handler only rejects a font but not reports the reason. For a kernel component like GDI, it is not a bad idea.

Shahab Siavash

Shahab Siavash said:

Thanks, I will keep this in mind and do that for sure, but yet again it's not about my font or my experience solely, when you search "not a valid font in Windows" you get 122,000,000 results. There are pages on Font.com and Fontsmith,... about this error, so again I don't think it is a font-related problem.
My point from the beginning was to find out what's the issue with Windows Font Viewer. Obviously I couldn't make it clear enough. 

To be clear: Windows Font Viewer rejects a font only when GDI rejects it.
Current GDI error handler only rejects a font but not reports the reason. For a kernel component like GDI, it is not a bad idea.

Thanks a lot. I only have one question though: Since the only reason is GDI rejection, how come a single font file opens on a PC with Windows 10 and yet the same font can't be installed on another system with Windows 10? Logically it must not occur.
As I mentioned before you got different results from people with the same Windows version.
On top of the frustration that users have to feel, I think this is a very bad publicity for freelance type designers, because the font actually is not corrupt, yet the user can't install it and obviously you can't explain to them that it's a Windows GDI thing, because they paid for a font and they want to use it anyhow.