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supportFor basic simple use from Gutenberg block to a small pdf media page – I get the following results: FireFox – works Chome – gray frame but no document loading Safari – gray frame but no document loading I tried browser cache clear ,and site’s litespeed purge all. Does not work. So I reverted to v3.0.2 to solve problem. The page I need help with: [ log in to see the link]
I’m not seeing PDFjs loading at that URL. Do you have another URL where I can see the issue?
Oh, I found the link to the PDF. It loads in Chrome and Safari for me.
Chances are it’s a caching issue somewhere. I try hard to prevent caching issue, but they keep popping up. Could be in your browser, in a caching plugin, in object or other server side caching, or in a CDN like Cloudflare. There are so many levels of caching sometimes that pinpointing the issue can be difficult.
So I was trying to be clear. My site can’t use 3.0.3.1 so I am not using it. I am using the last known working version on my site: 3.0.2. So I put the page where I see the problem, and thanks to those that found the gutenberg block that opens the PDF.js page. But of course it works, I am not on 3.0.3.1 because my users would then get no working pdf pages. And, before posting this thread I cleared every known cache I can find. So if no one else sees the problem with their typical/any PDF’s loading on 3.0.3.1 then fine, just close the call. But I can’t use this version. Very frustrating since PDF.js is a great plugin. I will close the call myself in a week or so if it magically starts working, when I have tested on more machines while temporarily going to the “suspicious” version 3.0.3.1
I can’t re-create any issues locally, and without an error message, it’s hard to fix. Pretty sure it’s related to caching, and I’ll need to rebuild the plugin to try and get around it.
Thank you for your review and mindshare on this issue. In my initial report, I described Firefox as working fine with PDF.js v3.0.3.1 – Just Chrome and Safari show only a gray background typical during a PDF loading. But on these two browsers the PDF never loads, no progress bar shown for typical loading, no error on screen, and no error_log entry to my webserver, and browser refresh button does not help, but the browser back button shows that the browsers are still responsive. Maybe my Mac with the latest super aggressive security update MacOS v26.3.1 (a) might be at fault. I am willing to confirm that a Windows PC does or does not show this annoying problem when I get a chance.
Hello, After updating to version 3.0.3.1, I also only see a grey screen. The PDF file is no longer displayed. I’ve tried everything to do with caches, but it’s not helping. The problem remains. This isn’t a normal occurrence. I never used to have this sort of problem after an update.
Do you have a URL to share where I can see the issue? This reply was modified 2 months ago by Thomas McMahon .
Also, can anyone open their browser console and see if there are any error messages? https://balsamiq.com/support/faqs/browser-console/
Hello, It seems to have been fixed for me now. Thank you.
I am having the same issue in Edge browser, after the latest update. Browser console error: app.js:1371 An error occurred while loading the PDF. PDF.js v5.5.207 (build: 527964698) Message: The API version “5.5.207” does not match the Worker version “5.4.449”. There is another issue when editing the page in wp-admin that has been going on for a while now. Instead of seeing the pdf I see “Forbidden – You don’t have permission to access this resource.” The pdf still displayed correctly on the public page, though, until the latest update to the plugin. Quick edit: this is only occurring in Edge – The pdf displays correctly in Chrome and Firefox. This reply was modified 2 months ago by rmarkb . This reply was modified 2 months ago by rmarkb .
I posted a test page last night on my website to verify PDF.js works as it should. I have verified last night that version 3.03.1 is working just fine on my Mac and on my Windows 11 boxes using these browsers: Chrome, Safari, and Firefox. My PDF.js test page to demonstrates PDF.js v3.0.3.1 : https://www.biophysicslab.com/2026/03/24/temp-post-to-test-pdf-loading/ The “big” confusion for me: After upgrading from 3.02 to 3.0.3.1 I cleared every cache I could think of: browsers, WordPress, and LiteSpeed cache. But this did not help. What did help was clearing the browser “history”. Turns out this does more than just remove web pages. Note from Gemini AI: Clearing browser history forced the browser to discard stored session data and re-evaluate active plugin permissions/URL mappings, whereas a basic cache clear often only removes temporary files, leaving persistent session data or corrupted, indexed page states that caused the PDF.js plugin to fail. Persistent State Issues: Even if temporary images/files are cleared, browsers store "history" (session state, localStorage, indexDB) which can retain older instructions that conflict with new plugins.Active Content vs. Temporary Files:Clearing "Cache" often just removes images and script files. Clearing "Browsing History" often forces a refresh of the page structure, cookies, and active session state, which allows the new viewer to take control.Redirect Confusion: The old viewer might have been flagged in the browser's history database to handle specific PDF file paths, requiring a full history wipe to break that association. Essentially, the plugin required a full reset of the browser's memory, not just a clearing of its temporary storage. This reply was modified 2 months ago by Ron Fredericks . This reply was modified 2 months ago by Ron Fredericks .
What AI gave you that? And what browser do you use? That’s not how caches works, but I’m glad it worked for you. It seems more like the browser cleared some cache, but not all of it. I have a new version that tries to break even more caches, but it’s hard to say it’ll do any different.
app.js:1371 An error occurred while loading the PDF. PDF.js v5.5.207 (build: 527964698) Message: The API version “5.5.207” does not match the Worker version “5.4.449”. That’s definitely a caching issue. I have an update to try to get around that, but not sure what’s caching things so much that it’s causing these issues.
I upgraded to v3.0.4 and it works fine. Thanks for working on my support question in a timely manner. I have updated my “PDF.js Test Page” to reflect the updated version. I plan to keep the page link active permanently so you and others can refer to it for testing. Over time I will keep the version title accurate in the heading: https://www.biophysicslab.com/2026/03/25/temp-post-to-test-pdf-loading/ Problem solved.
I still don’t understand how clearing your history would make a difference. But glad it’s working.
I’m not seeing PDFjs loading at that URL. Do you have another URL where I can see the issue?
Oh, I found the link to the PDF. It loads in Chrome and Safari for me.
Chances are it’s a caching issue somewhere. I try hard to prevent caching issue, but they keep popping up. Could be in your browser, in a caching plugin, in object or other server side caching, or in a CDN like Cloudflare. There are so many levels of caching sometimes that pinpointing the issue can be difficult.
So I was trying to be clear. My site can’t use 3.0.3.1 so I am not using it. I am using the last known working version on my site: 3.0.2. So I put the page where I see the problem, and thanks to those that found the gutenberg block that opens the PDF.js page. But of course it works, I am not on 3.0.3.1 because my users would then get no working pdf pages. And, before posting this thread I cleared every known cache I can find. So if no one else sees the problem with their typical/any PDF’s loading on 3.0.3.1 then fine, just close the call. But I can’t use this version. Very frustrating since PDF.js is a great plugin. I will close the call myself in a week or so if it magically starts working, when I have tested on more machines while temporarily going to the “suspicious” version 3.0.3.1
I can’t re-create any issues locally, and without an error message, it’s hard to fix. Pretty sure it’s related to caching, and I’ll need to rebuild the plugin to try and get around it.
Thank you for your review and mindshare on this issue. In my initial report, I described Firefox as working fine with PDF.js v3.0.3.1 – Just Chrome and Safari show only a gray background typical during a PDF loading. But on these two browsers the PDF never loads, no progress bar shown for typical loading, no error on screen, and no error_log entry to my webserver, and browser refresh button does not help, but the browser back button shows that the browsers are still responsive. Maybe my Mac with the latest super aggressive security update MacOS v26.3.1 (a) might be at fault. I am willing to confirm that a Windows PC does or does not show this annoying problem when I get a chance.
Hello, After updating to version 3.0.3.1, I also only see a grey screen. The PDF file is no longer displayed. I’ve tried everything to do with caches, but it’s not helping. The problem remains. This isn’t a normal occurrence. I never used to have this sort of problem after an update.
Do you have a URL to share where I can see the issue? This reply was modified 2 months ago by Thomas McMahon .
Also, can anyone open their browser console and see if there are any error messages? https://balsamiq.com/support/faqs/browser-console/
Hello, It seems to have been fixed for me now. Thank you.
I am having the same issue in Edge browser, after the latest update. Browser console error: app.js:1371 An error occurred while loading the PDF. PDF.js v5.5.207 (build: 527964698) Message: The API version “5.5.207” does not match the Worker version “5.4.449”. There is another issue when editing the page in wp-admin that has been going on for a while now. Instead of seeing the pdf I see “Forbidden – You don’t have permission to access this resource.” The pdf still displayed correctly on the public page, though, until the latest update to the plugin. Quick edit: this is only occurring in Edge – The pdf displays correctly in Chrome and Firefox. This reply was modified 2 months ago by rmarkb . This reply was modified 2 months ago by rmarkb .
I posted a test page last night on my website to verify PDF.js works as it should. I have verified last night that version 3.03.1 is working just fine on my Mac and on my Windows 11 boxes using these browsers: Chrome, Safari, and Firefox. My PDF.js test page to demonstrates PDF.js v3.0.3.1 : https://www.biophysicslab.com/2026/03/24/temp-post-to-test-pdf-loading/ The “big” confusion for me: After upgrading from 3.02 to 3.0.3.1 I cleared every cache I could think of: browsers, WordPress, and LiteSpeed cache. But this did not help. What did help was clearing the browser “history”. Turns out this does more than just remove web pages. Note from Gemini AI: Clearing browser history forced the browser to discard stored session data and re-evaluate active plugin permissions/URL mappings, whereas a basic cache clear often only removes temporary files, leaving persistent session data or corrupted, indexed page states that caused the PDF.js plugin to fail. Persistent State Issues: Even if temporary images/files are cleared, browsers store "history" (session state, localStorage, indexDB) which can retain older instructions that conflict with new plugins.Active Content vs. Temporary Files:Clearing "Cache" often just removes images and script files. Clearing "Browsing History" often forces a refresh of the page structure, cookies, and active session state, which allows the new viewer to take control.Redirect Confusion: The old viewer might have been flagged in the browser's history database to handle specific PDF file paths, requiring a full history wipe to break that association. Essentially, the plugin required a full reset of the browser's memory, not just a clearing of its temporary storage. This reply was modified 2 months ago by Ron Fredericks . This reply was modified 2 months ago by Ron Fredericks .
What AI gave you that? And what browser do you use? That’s not how caches works, but I’m glad it worked for you. It seems more like the browser cleared some cache, but not all of it. I have a new version that tries to break even more caches, but it’s hard to say it’ll do any different.
app.js:1371 An error occurred while loading the PDF. PDF.js v5.5.207 (build: 527964698) Message: The API version “5.5.207” does not match the Worker version “5.4.449”. That’s definitely a caching issue. I have an update to try to get around that, but not sure what’s caching things so much that it’s causing these issues.
I upgraded to v3.0.4 and it works fine. Thanks for working on my support question in a timely manner. I have updated my “PDF.js Test Page” to reflect the updated version. I plan to keep the page link active permanently so you and others can refer to it for testing. Over time I will keep the version title accurate in the heading: https://www.biophysicslab.com/2026/03/25/temp-post-to-test-pdf-loading/ Problem solved.
I still don’t understand how clearing your history would make a difference. But glad it’s working.