HTTP 504 response to all /xfdf/merge POST requests

PDF.js Express Viewer
UI version 6.3.3
Core version 6.3.3

All API requests have stopped working and responding with 504 after a VERY long interval (10 - 50 seconds).

var response = await fetch('', {
                             mode: 'no-cors',
                            method: 'post',
                            body: data
                        }).then(resp => resp.json());

Hello, I’m Ron, an automated tech support bot :robot:

While you wait for one of our customer support representatives to get back to you, please check out some of these documentation pages:


Hey there,

I cannot reproduce this issue - can you please send me a document you are having issues with?


I have used this editor last 2 3 years . Merge API stopped working the last few days, Now showing errors like the below-attached document.

Please check the below URL to find the issue.

Email :

Password : demoinspector123!@#

Dear Logan,

Awaiting quick response to resolve the issue. suddenly it stopped working and we r in the dark with no proper support.

Hi there,

I just checked the site you showed me and took a look at the network request to the merge API. It looks like you are providing a file URL that looks like so:

The URL is timing out when making requests to it which means the issue is coming from your end. Please make sure your server is running correctly and is able to respond to requests.