Hello, So I'm able to generate a pdf from fpdf just fine in FireFox, but it sometimes works in Chrome, but not all always. I was wondering if this has something to do with the browser and fpdf's code, or if there is a way to fix this.

It shouldn't have anything to do with the browser as you will be generating the pdf on the server. On Firefox, it would probably end up being PDFJS that renders the PDF and on Chrome it would be their PDF engine, PDFium. So maybe one likes the output of FPDF more than the other? You can always try tacking on a Content-Disposition: inline header to see if it helps.

Thanks for the reply, I found the error. For anyone who has this issue, with fpdfs output function, you can't output anything else besides the output function.