Can I set the filename of a PDF object displayed in Chrome?

Question

In my Vue app I receive a PDF as a blob, and want to display it using the browser's PDF viewer.

I convert it to a file, and generate an object url:

const blobFile = new File([blob], `my-file-name.pdf`, { type: 'application/pdf' })
this.invoiceUrl = window.URL.createObjectURL(blobFile)

Then I display it by setting that URL as the data attribute of an object element.

<object
  :data="invoiceUrl"
  type="application/pdf"
  width="100%"
  style="height: 100vh;">
</object>

The browser then displays the PDF using the PDF viewer. However, in Chrome, the file name that I provide (here, my-file-name.pdf) is not used: I see a hash in the title bar of the PDF viewer, and when I download the file using either 'right click -> Save as...' or the viewer's controls, it saves the file with the blob's hash (cda675a6-10af-42f3-aa68-8795aa8c377d or similar).

The viewer and file name work as I'd hoped in Firefox; it's only Chrome in which the file name is not used.

Is there any way, using native Javascript (including ES6, but no 3rd party dependencies other than Vue), to set the filename for a blob / object element in Chrome?

[edit] If it helps, the response has the following relevant headers:

Content-Type: application/pdf; charset=utf-8
Transfer-Encoding: chunked
Content-Disposition: attachment; filename*=utf-8''Invoice%2016246.pdf;
Content-Description: File Transfer
Content-Encoding: gzip

Answer 1

Chrome's extension seems to rely on the resource name set in the URI, i.e the file.ext in protocol://domain/path/file.ext.

So if your original URI contains that filename, the easiest might be to simply make your <object>'s data to the URI you fetched the pdf from directly, instead of going the Blob's way.

Now, there are cases it can't be done, and for these, there is a convoluted way, which might not work in future versions of Chrome, and probably not in other browsers, requiring to set up a Service Worker.

As we first said, Chrome parses the URI in search of a filename, so what we have to do, is to have an URI, with this filename, pointing to our blob:// URI.

To do so, we can use the Cache API, store our File as Request in there using our URL, and then retrieve that File from the Cache in the ServiceWorker.

Or in code,

From the main page

// register our ServiceWorker
navigator.serviceWorker.register('/sw.js')
  .then(...
...

async function displayRenamedPDF(file, filename) {
  // we use an hard-coded fake path
  // to not interfere with legit requests
  const reg_path = "/name-forcer/";
  const url = reg_path + filename;
  // store our File in the Cache
  const store = await caches.open( "name-forcer" );
  await store.put( url, new Response( file ) );

  const frame = document.createElement( "iframe" );
  frame.width = 400
  frame.height = 500;
  document.body.append( frame );
  // makes the request to the File we just cached
  frame.src = url;
  // not needed anymore
  frame.onload = (evt) => store.delete( url );
}

In the ServiceWorker sw.js

self.addEventListener('fetch', (event) => {
  event.respondWith( (async () => {
    const store = await caches.open("name-forcer");
    const req = event.request;
    const cached = await store.match( req );
    return cached || fetch( req );
  })() );
});

Live example (source)

Edit: This actually doesn't work in Chrome...

While it does set correctly the filename in the dialog, they seem to be unable to retrieve the file when saving it to the disk...
They don't seem to perform a Network request (and thus our SW isn't catching anything), and I don't really know where to look now.
Still this may be a good ground for future work on this.

---

And an other solution, I didn't took the time to check by myself, would be to run your own pdf viewer.

Mozilla has made its js based plugin pdf.js available, so from there we should be able to set the filename (even though once again I didn't dug there yet).

---

And as final note, Firefox is able to use the name property of a File Object a blobURI points to. So even though it's not what OP asked for, in FF all it requires is

const file = new File([blob], filename);
const url = new URL(blob);
object.data = url;

Answer 2

In Chrome, the filename is derived from the URL, so as long as you are using a blob URL, the short answer is "No, you cannot set the filename of a PDF object displayed in Chrome." You have no control over the UUID assigned to the blob URL and no way to override that as the name of the page using the object element. It is possible that inside the PDF a title is specified, and that will appear in the PDF viewer as the document name, but you still get the hash name when downloading.

This appears to be a security precaution, but I cannot say for sure.

Of course, if you have control over the URL, you can easily set the PDF filename by changing the URL.

Answer 3

I believe Kaiido's answer expresses, briefly, the best solution here:

"if your original URI contains that filename, the easiest might be to simply make your object's data to the URI you fetched the pdf from directly"

Especially for those coming from this similar question, it would have helped me to have more description of a specific implementation (working for pdfs) that allows the best user experience, especially when serving files that are generated on the fly.

The trick here is using a two-step process that perfectly mimics a normal link or button click. The client must (step 1) request the file be generated and stored server-side long enough for the client to (step 2) request the file itself. This requires you have some mechanism supporting unique identification of the file on disk or in a cache.

Without this process, the user will just see a blank tab while file-generation is in-progress and if it fails, then they'll just get the browser's ERR_TIMED_OUT page. Even if it succeeds, they'll have a hash in the title bar of the PDF viewer tab, and the save dialog will have the same hash as the suggested filename.

Here's the play-by-play to do better:

• You can use an anchor tag or a button for the "download" or "view in browser" elements

• Step 1 of 2 on the client: that element's click event can make a request for the file to be generated only (not transmitted).

• Step 1 of 2 on the server: generate the file and hold on to it. Return only the filename to the client.

• Step 2 of 2 on the client:

  • If viewing the file in the browser, use the filename returned from the generate request to then invoke window.open('view_file/<filename>?fileId=1'). That is the only way to indirectly control the name of the file as shown in the tab title and in any subsequent save dialog.
  • If downloading, just invoke window.open('download_file?fileId=1').

• Step 2 of 2 on the server:

  • view_file(filename, fileId) handler just needs to serve the file using the fileId and ignore the filename parameter. In .NET, you can use a FileContentResult like File(bytes, contentType);
  • download_file(fileId) must set the filename via the Content-Disposition header as shown here. In .NET, that's return File(bytes, contentType, desiredFilename);

client-side download example:

download_link_clicked() {
                // show spinner   
                ajaxGet(generate_file_url,
                    {},
                    (response) => {
                        // success!                        
                        // the server-side is responsible for setting the name 
                        // of the file when it is being downloaded                         
                        window.open('download_file?fileId=1', "_blank");
                        // hide spinner
                    },
                    () => { // failure
                       // hide spinner
                       // proglem, notify pattern
                    },
                    null
                );

client-side view example:

view_link_clicked() { 
                // show spinner
                ajaxGet(generate_file_url,
                    {},
                    (response) => {
                        // success!
                        let filename = response.filename;      
                        // simplest, reliable method I know of for controlling 
                        // the filename of the PDF when viewed in the browser
                        window.open('view_file/'+filename+'?fileId=1')
                        // hide spinner
                    },
                    () => { // failure
                       // hide spinner
                       // proglem, notify pattern
                    },
                    null
                );