Multiplex not working for revealjs output

[DaniMori]

Description

It seems like the "multiplex" plugin does not work anymore since the last time I used it (about a year ago), or at least doesn't work automatically.

When trying to render a revealjs presentation with multiplex: true I get the following error message:

ERROR: Error attempting to provision multiplex token from 'https://reveal-multiplex.glitch.me/': Unexpected token '<', "<!DOCTYPE "... is not valid JSON

(you can simply reproduce the error with:)

---
format:
  revealjs:
    multiplex: true
---

Hello World!

When browsing to the URL in the error, it seems there's nothing served there indeed: The "Glitch" website says that Glitch project hosting is no longer available. 😞

Is there a way to configure a different server to grab the multiplex files, or something like that? I want to make sure it's worth reporting this before opening an issue.

Thanks!

[mcanouil]

You need to upgrade Quarto and render again.
This was a change from Pandoc that was addressed in recent versions.
Old Reveal.js need to be re-rendered to use the new server.

I need to check, but glitch might be the up to date version.
Would you mind sharing quarto check output and/or the exact version of Quarto CLI used?

[DaniMori]

Sure! Here you are both:

$ quarto -v
1.8.25

$ quarto check
Quarto 1.8.25
[>] Checking environment information...
      Quarto cache location: C:\Users\Daniel Morillo\AppData\Local\quarto
[>] Checking versions of quarto binary dependencies...
      Pandoc version 3.6.3: OK
      Dart Sass version 1.87.0: OK
      Deno version 2.3.1: OK
      Typst version 0.13.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
      Version: 1.8.25
      Path: C:\Program Files\RStudio\resources\app\bin\quarto\bin
      CodePage: 1252

[>] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: (not installed)

[>] Checking LaTeX....................OK
      Using: TinyTex
      Path: C:\ProgramData\TinyTeX\bin\windows\
      Version: 2024

[>] Checking Chrome Headless....................OK
      Using: Chrome found on system
      Path: C:\Program Files\Google\Chrome\Application\chrome.exe
      Source: Windows Registry

[>] Checking basic markdown render....OK

[>] Checking Python 3 installation....OK
      Version: 3.14.2
      Path: C:/Users/Daniel Morillo/AppData/Local/Python/pythoncore-3.14-64/python.exe
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with py -m pip install jupyter

[>] Checking R installation...........OK
      Version: 4.5.2
      Path: C:/PROGRA~1/R/R-45~1.2
      LibPaths:
        - C:/Users/Daniel Morillo/Documents/Workspace/git-workshop/renv/library/windows/R-4.5/x86_64-w64-mingw32
        - C:/Users/Daniel Morillo/AppData/Local/R/cache/R/renv/sandbox/windows/R-4.5/x86_64-w64-mingw32/ebc25411
      knitr: 1.50
      rmarkdown: 2.29

[>] Checking Knitr engine render......OK

FYI, I just updated to 1.9.37, and it worked! So time to close this thread I guess, thanks a lot!

[mcanouil]

So, you are using the new server.

Note that if you don't want to rely on third parties for this, you can quite easily setup your own multiplex server following the documentation: https://quarto.org/docs/presentations/revealjs/presenting.html#multiplex-server

[DaniMori]

Ok, I understood the problem was with providing the plugin code, but according to what you say, it must be the multiplex server instead. I wasn't intending to set my own server but go for the straightforward option, but thanks a lot for clarifying this, it will definitely help troubleshooting if it happens again 🙂