21
Brother Printer
Severity: ModerateWhat Does This Error Mean?
Brother error 21 is a print data error meaning the printer received data it cannot understand or process. The job was sent but something about the file or format is incompatible with the printer. No damage is done — you just need to fix the data or how it is being sent.
Affected Models
- Brother HL-L2390DW
- Brother MFC-L2710DW
- Brother MFC-L2750DW
- Brother DCP-L2550DW
- Brother HL-L3270CDW
Common Causes
- The print job was sent in a file format or printer language the printer does not support
- A corrupted or incomplete file was sent — the data was cut off or scrambled in transit
- The wrong printer driver is installed, causing the computer to send incompatible data
- The document was sent from an app that does not properly support the printer's language (PCL or PostScript)
- The printer and computer are using different print protocol settings over a network connection
How to Fix It
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Cancel all jobs in the print queue on your computer and restart the printer.
Clearing the queue removes the bad job that triggered the error. The printer cannot move on until the queue is empty.
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Make sure the correct Brother printer driver is installed for your exact model.
Download the driver directly from brother.com — search for your model number. Installing the wrong driver is a common cause of error 21.
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Try printing a test page from inside the printer's own menu (not from your computer).
If the printer's own test page prints fine, the hardware is working. The problem is with the data your computer is sending.
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Try printing a different, simpler document — a basic Word file or plain text.
If the simple document prints fine, the original document has a format or content issue. Try saving it as a PDF and printing that instead.
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If you are printing over a network, check the print protocol settings. Make sure the printer and driver are both set to use the same language — typically PCL.
Mixing PCL and PostScript settings between driver and printer is a known cause of data errors on Brother network printers.
When to Call a Professional
Error 21 is almost always resolved by fixing the driver or the document being printed. Hardware involvement is rare. If reinstalling the driver and testing multiple documents all produce error 21, contact Brother support for further diagnostics.
Frequently Asked Questions
What is the difference between error 20 and error 21 on Brother printers?
Error 20 is about the printer running out of memory while processing a job. Error 21 is about the printer receiving data it simply cannot read or interpret. Both are software issues, but the fixes are slightly different — 21 is more often a driver or file format problem.
Does printing from a USB drive instead of a computer fix error 21?
It can help. If the error is caused by a driver or computer communication issue, printing a PDF directly from a USB drive bypasses both. However, if the file itself is the problem, you will get the same error from USB.
Why do some files print fine but others get error 21?
Different applications create print data differently. A file from a design application like Illustrator or InDesign may use fonts or vector elements that your Brother printer struggles to interpret. Saving the file as a flattened PDF often resolves this.