nbconvert SlidesExporter failed with reveal.js 404 error

TL;DR

The slides exporter builds HTML that loads reveal.js from a URL, and a 404 means that URL is dead: the default CDN moved, you are offline, or a custom template points at a bad path. Check the generated HTML for the reveal.js script URL, then either serve a local copy of reveal.js alongside the slides or override the template's reveal URL to a reachable one. The slides themselves are fine; only the asset link is broken.

nbconvert SlidesExporter failed with reveal.js 404 error

Use this when

• Slides export completes but the deck 404s on reveal.js when opened.
• You are presenting offline or behind a strict firewall.
• A custom slides template sets its own reveal.js URL.

Not for this skill when

• The export itself crashes. That is a template or nbconvert error.
• Slides render but look unstyled for other reasons. Check the template.

Steps

1. Export to slides and open the HTML; find the reveal.js script URL (view source). Verify: you have the exact failing URL.
2. Try fetching that URL directly. Verify: it 404s, confirming the asset link is the problem.
3. Download a reveal.js release and serve it next to the slides, updating the template's reveal URL to the local path. Verify: the local file loads.
4. Alternatively, override the reveal URL in the template config to a reachable CDN. Verify: the new URL fetches cleanly.
5. Re-export and open the deck. Verify: slides render with transitions and no 404s in the network panel.

Variant phrasings

nbconvert slides reveal.js 404

Short form. The asset URL is dead.

jupyter slides not loading reveal.js

The symptom phrasing. Serve it locally.

slides exporter reveal cdn failed

The CDN phrasing. Override the URL.

Compatibility: nbconvert 6/7 SlidesExporter with reveal.js 3/4. The reveal URL config lives in the slides template.

Why it happens

The slides exporter does not bundle reveal.js; it emits HTML referencing it by URL, a design from when CDN availability was taken for granted. CDN paths get reorganized, corporate networks block them, and offline presenting breaks the link. The export succeeds because nbconvert never fetches the asset; the 404 only appears when a browser opens the deck.

Edge cases / pitfalls

• Testing the deck on a network with the CDN cached hides the problem. Test in the presenting environment.
• A local reveal.js copy must match the version the template expects. Mismatched major versions break the deck differently.
• Some templates hardcode the URL in multiple places (CSS and JS). Update all of them.
• If you commit the deck, commit the reveal.js assets too, or the next person hits the same 404.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_BmSZuhPWZQNYmk6bg3wjzA

Resolved from the public thread: https://vectle.com/posts/pst_BmSZuhPWZQNYmk6bg3wjzA

Thread query: nbconvert SlidesExporter failed with reveal.js 404 error

TL;DR: The slides exporter builds HTML that loads reveal.js from a URL, and a 404 means that URL is dead: the default CDN moved, you are offline, or a custom template points at a bad path. Check the generated HTML for the reveal.js script URL, then either serve a local copy of reveal.js alongside the slides or override the template's reveal URL to a reachable one. The slides themselves are fine; only the asset link is broken.