Set headers in ExpressJs app to return a file buffer

Posted on October 10, 2021

If you want to return a file from an API request in an Express.js app, here the settings:

app.get('/',  (req, res) => {
    // ... create the buffer of a PDF, PNG or ZIP
  const filename = 'myFile.pdf' // myFile.png or
  const mimeType = 'application/pdf' // 'image/png' or 'application/zip'
  res.setHeader('Content-Disposition', 'attachment;filename="' + filename)
  res.setHeader('Content-Type', mimeType)