Hi jean-louis, as you've seen, Firefox's built-in PDF viewer does not work with all PDF features supported by external programs and plug-in based viewers; there are lot of issues on file to improve it.

In this case, it is difficult to understand why the barcode is not displayed based on a screenshot. It could be that the bar code is laid out using a custom font that Firefox isn't rendering, or it may use drawing instructions that Firefox is rendering in an unexpected location, or perhaps it is an image encoding that Firefox can't render.

Is there a PDF demonstrating this problem that you can link to? Note that replies containing URLs go into the spam moderation queue, so it's normal to have a delay before the post appears.

Hi jlcher2000, You can find the file link here : https://drive.google.com/file/d/1xXpKgyTTOT63mXhnUrmt6JTL43EKC5Gt/view?usp=sharing Sorry, i don't speak english very well... Thank you. Jean-Louis

1. Open a file in a Windows application.
2. Choose File > Print.
3. Choose Adobe PDF as the printer in the Print dialog box. To customize the Adobe PDF printer setting, click the Properties (or Preferences) button. ...
4. Click Print. Type a name for your file, and click Save.

https://helpx.adobe.com/in/acrobat/using/print-to-pdf.html

1. Open a file in a Windows application.
2. Choose File > Print.
3. Choose Adobe PDF as the printer in the Print dialog box. To customize the Adobe PDF printer setting, click the Properties (or Preferences) button. ...
4. Click Print. Type a name for your file, and click Save.

https://helpx.adobe.com/in/acrobat/using/print-to-pdf.html

Hi Jean-Louis, I downloaded the PDF and opened it in Firefox and the bar code does appear on mine. I wonder if there is some reason the bar code is blocked when viewing the PDF on the original site. Does it make any difference for you if you open the downloaded PDF in Firefox?

No problem with seeing the barcode in Firefox both on the website and when downloaded.

I can't find the barcode in the DOM, so I assume it is somewhere drawn on canvas and doesn't show in the inspector.

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• hold down the Shift key and left-click the Reload button
• press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• press "Command + Shift + R" (Mac)

Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" for websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data: "Manage Data"

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

I have 2 Windows computers with Windows 10 Pro and Firefox V79.0 64bits - On the first (Windows 10 v1909 - AMD Athlon X2 5000+), i cannot read the bar code - On the second (MS Surface 3), i can read the bar code May be because of the graphic card ???

- Cache Cleared - Cookies removed - Extension modules disabled - Start Firefox in Safe Mode >>> I see the bar code - Start Firefox in normal mode >>> i don't see the bar code

Was it solved by either disabling hardware acceleration in normal mode, or updating the graphics card drivers?

Disabling Firefox from using hardware acceleration is a potential workaround for incompatibilities between Firefox and your graphics card/chipset driver software. This article describes where to make that change: Firefox's performance settings. This will take effect the next time you exit Firefox and start it up again. Any difference?

Since hardware acceleration improves the appearance of fonts and animations, you may want to check whether graphics card/chipset driver updates are available for your system. This article suggests safe ways to do that: Upgrade your graphics drivers to use hardware acceleration and WebGL.

Are you possibly using content blocking extensions ?

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

I only use Ublock Origin. Idem when disabled.

My graphic card is old (nVidia GEforce 210) and its driver is up to date. Bar code is OK when hardware acceleration is disabled. Thank you for your help. Jean-Louis