Closed Bug 1666914 Opened 1 year ago Closed 1 year ago

Printer Paper Size Mismatch


(Core :: Printing: Setup, defect)

80 Branch





(Reporter: invicta537, Unassigned)


(Whiteboard: [print2020])


(1 file)

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:80.0) Gecko/20100101 Firefox/80.0

Steps to reproduce:

I have started using a new HP Smart Tank Plus 559 printer and I am using Firefox from a Windows 10 PC. I am plagued with Paper Mismatch errors when printing emails from Firefox. This problem seems to be confined to Firefox, as it does not happen when using other browsers, e.g. MS Edge. In the printing dialogue box under Printing Preferences, the paper size shows "Letter", whereas I am using A4 in the printer, and this mismatch causing the problem. I can change the paper size in Printing Preferences from Letter to A4, but I have to do this for every job seperately as the paper size setting always reverts to "Letter". This is totally impracticable. I am submitting this Bug here at the request of your Printing Developer Jonathan Watt after I requested help on

Actual results:

The print job stops with the error message Paper Size Mismatch after the 1st page, and printing will not continue or even move on to the next job until the error is cancelled from the printer's control panel. This means I have to be working next to the printer and cannot print remotely. I have tried resetting all Firefox printer settings and the problem still happens when opening Firefox in Safe Mode.

Expected results:

I should be able to set the paper size to default to A4 to eliminate "Paper Mismatch" errors from the printer.

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Component: Untriaged → Printing: Setup
Product: Firefox → Core

Original SUMO question:

Thanks for re-reporting this here. Can you open the page about:support, click on the "Copy text to clipboard" button, click "Attach new file" on this bug report, and then paste and submit that here. Maybe also check over the contents of the paste before submitting it to make sure there's nothing in there that you don't want to share publicly (I don't think there should be, but check for yourself).

It's probably worth updating to Firefox 81 first. I don't expect doing that to fix the issue, but we might as well be testing the current release.

A couple of other things that would be helpful to know:

Where are these emails being printed from? Gmail, Hotmail, something else?

You say that you can change the paper size in Printing Preferences from Letter to A4. Does that get the entire print job to complete successfully? Or does that only get the first page to print and delay the mismatch error until after that first page whereas before the error would occur before even the first page?

Just to update you, I received an answer from to my original cry for help on as follows:

"(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.
(2) In the search box in the page, type or paste paper_data and pause while the list is filtered
Firefox should list the value for all of your printers. My general understanding is:
1 => letter
9 => A4
If your printer with A4 paper does not have this value set to 9, try editing it:
Double-click the preference to display an editing field, and change the value to 9 then press Enter or click the blue check mark button to save the change."

So I followed this suggestion and my current printer value was 9 and I checked that the problem still existed.
I noticed that two old printers that did not have the same issue were showing 1 and 6. I tried changing to both of these and the problem persisted.
I changed my current printer back to 9 and surprisingly it seems to have cleared the problem.

This appears to have solved the issue, but I am happy to answer your questions as above:

  1. I have updated to the latest Firefox 81.0 64Bit.
  2. I receive most of my emails from through my account at, but I also use gmail and experience the same issues. If I print the same emails using MS Edge browser, there is no problem. I don't really want to switch to Edge.
  3. When I change the paper size in Printing Preferences from Letter to A4, the whole job will print. But the setting reverts to Letter for the next job.

If you don't mind, I am reluctant to try anything else for now, but I will carry on using the printer to see whether I have a permanent fix, or if the problems return. So please keep this Bug Report Open and I will update it in a couple of days to let you know what is happening.

Thanks very much for your help.

Severity: -- → S2
Whiteboard: [print2020]

Hello Jonathan Watt

Just to update my Comment 5 above, I have continued using my printer for several days now and this Paper Mismatch problem has not happened again.

Following the suggestion by jscher2000 on, I found that the value for my printer under '''paper_data''' was already 9, but trying other values and then changing it back to 9 appears to have somehow cleared the issue.

I don't understand this, but it worked. So thank you very much for replying and offering to help.


No worries, CSH! Thanks for taking the time to file this report here and to go through all the diagnostic steps. For bug reports where we don't come to a definative conclusion about what went wrong or what fixed things we mark them as "incomplete", so I'll do that now. Good luck, and let us know if you have any further printing problems.

Closed: 1 year ago
Resolution: --- → INCOMPLETE
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