SfPdfViewer.network fails to render even simple public PDF on Flutter Web (dummy.pdf)

[Tatsuya4610]

Bug description

Issue Summary

SfPdfViewer.network fails to load a simple, publicly available PDF file on Flutter Web. Even with basic English-only PDF content, the viewer shows a grey screen and triggers the onDocumentLoadFailed callback.

URL Used

https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf

Observations

• The PDF is publicly accessible and contains only simple English text.

• It has valid Content-Length and Content-Type: application/pdf headers.

• There are no CORS restrictions — the PDF opens fine in a browser.

• On Flutter Web, the viewer fails with the following error:

• The same PDF works perfectly when used with SfPdfViewer.network on Android and iOS.

Expected Behavior

The PDF should render correctly on Flutter Web, especially for such a simple, publicly available document.

Actual Behavior

A grey screen is shown and onDocumentLoadFailed is triggered with a vague error message.

Versions

• syncfusion_flutter_pdfviewer: ^29.1.41
• Flutter: 3.29.3 (Dart 3.7.2)
• Platform: Flutter Web (Chrome)

Note: I also tested with Flutter 3.27.4 and downgraded syncfusion_flutter_pdfviewer to 28.1.41, but the issue remained unchanged.

Suggestion

Please investigate why even basic PDFs (like the W3C dummy file) fail to render on Flutter Web with SfPdfViewer.network. A clearer error message or fallback guidance would also be helpful.

Steps to reproduce

1. Create a new Flutter project (or use an existing one).
2. Add the following dependency to your pubspec.yaml:

dependencies:
  syncfusion_flutter_pdfviewer: ^29.1.41

import 'package:flutter/material.dart';
import 'package:syncfusion_flutter_pdfviewer/pdfviewer.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('PDF Test')),
        body: SfPdfViewer.network(
          'https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf',
          onDocumentLoadFailed: (PdfDocumentLoadFailedDetails details) {
            print('${details.error}');
            print('${details.description}');
          },
        ),
      ),
    );
  }
}

Code sample

Code sample

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('PDF Test')),
        body: SfPdfViewer.network(
          'https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf',
          onDocumentLoadFailed: (PdfDocumentLoadFailedDetails details) {
            print('${details.error}');
            print('${details.description}');
          },
        ),
      ),
    );
  }
}

Screenshots or Video

Screenshots / Video demonstration

Stack Traces

Stack Traces

No stack trace was shown in the console.

The only available output came from the onDocumentLoadFailed callback of SfPdfViewer, which returned:

     onDocumentLoadFailed: (PdfDocumentLoadFailedDetails details) {
            print('error: ${details.error}');
            print('description: ${details.description}');
          },

print log

error: Error
description: There was an error opening this document.

On which target platforms have you observed this bug?

Web

Flutter Doctor output

Doctor output

flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.29.3, on macOS 15.4.1 24E263 darwin-arm64, locale ja-JP)
[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 16.3)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2022.3)
[✓] VS Code (version 1.98.2)
[✓] Connected device (4 available)
    ! Error: Browsing on the local area network for tatsuyaの iPhone. Ensure the device is unlocked and attached with a cable or associated
      with the same local area network as this Mac.
      The device must be opted into Developer Mode to connect wirelessly. (code -27)
[✓] Network resources

• No issues found!

[mmcquin]

Also seeing this issue using SfPdfViewer.memory

Flutter: 3.29.2
syncfusion_flutter_pdfviewer: ^28.2.12

Note that this is working fine when developing on localhost, it only becomes a problem when deployed. In my case, I am deployed to Firebase Hosting.

[mmcquin]

@Tatsuya4610 just ran a flutter clean, flutter build web --release, and then deployed and that resolved my issue. Have you given that a shot?

[Tatsuya4610]

@mmcquin

Thanks for the suggestion!

I did try running flutter clean, then flutter build web --release, and deployed the result via Firebase Hosting. Unfortunately, the issue still persists.

In my case, the PDF does not load even when running locally via flutter run -d chrome — the viewer shows only a grey screen, and onDocumentLoadFailed is triggered with the same error message as before:

The same behavior occurs after deployment as well.
You can check the deployed version here:
👉 https://moberly-co-jp.web.app/test_pdf_view

So this seems to be a reproducible issue across both local and deployed environments for me.
Let me know if there's anything else I can try!

Code

Scaffold(
      appBar: AppBar(title: Text('PDF Test')),
      body: SfPdfViewer.network(
        'https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf',
        onDocumentLoadFailed: (PdfDocumentLoadFailedDetails details) {
          print('${details.error}');
          print('${details.description}');
        },
      ),
    );

[mmcquin]

@Tatsuya4610 In troubleshooting, I changed to use the <script> associated with pre-4.0 PdfJs. I am not 100% sure if that had any impact, but you might be able to try that:

<script src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/2.11.338/pdf.min.js"></script> <script type="text/javascript"> pdfjsLib.GlobalWorkerOptions.workerSrc = "https://cdnjs.cloudflare.com/ajax/libs/pdf.js/2.11.338/pdf.worker.min.js"; </script>

[mmcquin]

@Tatsuya4610 I opened your app, and in inspecting the console, noticed a CORS failure. I see you mentioned that is not an issue, so I thought that was a little strange. Does that show up for you in console?

[Tatsuya4610]

@mmcquin
I really thought the previous PDF URL had no CORS restrictions, but I was wrong 😅
Using the following CORS-allowed URL worked perfectly:

👉 https://mozilla.github.io/pdf.js/web/compressed.tracemonkey-pldi-09.pdf

Thanks so much for pointing me in the right direction!

[immankumarsync]

Hi @Tatsuya4610,

We were able to replicate the reported issue where the SfPdfViewer widget is unable to load the PDF document from the following URL:
https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf

Upon further investigation, we found that the URL is blocked by the CORS policy. Please refer to the image below for your reference:

Could you please try loading a URL that is not blocked by CORS and let us know if the issue persists?

[Tatsuya4610]

@mmcquin @immankumarsync
Thanks for the update and for reproducing the issue!

You're absolutely right — the problem was indeed due to CORS restrictions on the original URL.
After switching to a CORS-allowed PDF URL, the issue was resolved and the document now loads correctly with SfPdfViewer.network.

Appreciate your help in pointing me in the right direction!