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What an asset is

An asset is any non-HTML file your deck references: images, GIFs, video, audio, 3D models (glTF/GLB/USDZ), shaders (GLSL/WGSL), CSS, JS modules, JSON data files, fonts. Slideless doesn’t have a hardcoded allow-list — whatever you put in the deck folder gets uploaded and served with the correct Content-Type.

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Supported formats

Slideless detects MIME types from file extensions. A sensible default table plus a few explicit overrides:
ExtensionContent-Type
.jpg / .jpegimage/jpeg
.pngimage/png
.webpimage/webp
.gifimage/gif
.svgimage/svg+xml
.hdrimage/vnd.radiance
.mp4video/mp4
.webmvideo/webm
.mp3 / .wav / .oggaudio/*
.glbmodel/gltf-binary
.gltfmodel/gltf+json
.usdzmodel/vnd.usdz+zip
.glsl / .wgsltext/plain; charset=utf-8
.woff2font/woff2
.wofffont/woff
.ttffont/ttf
.otffont/otf
.eotapplication/vnd.ms-fontobject
.htmltext/html; charset=utf-8
.csstext/css; charset=utf-8
.js / .mjs / .cjstext/javascript; charset=utf-8
.jsonapplication/json; charset=utf-8
.webmanifestapplication/manifest+json
unknownapplication/octet-stream
Bundling custom fonts with @font-face? See Custom fonts for the folder layout and the CSS snippet. If a format you need isn’t detected correctly, file an issue — overrides live in a single map in the CLI.

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Content-addressed storage

Every asset is stored at a path derived from its SHA-256: 
shared_presentations/{presentationId}/assets/sha256/{first-two-hex-chars}/{full-hash}
Three consequences:
  1. Integrity. The backend recomputes the hash server-side during upload. If the declared hash doesn’t match the received bytes, the blob is deleted and the upload is rejected with hash-mismatch — so a malicious client can’t smuggle corrupt content into another user’s namespace.
  2. Dedup across versions. Update a deck, keep the same hero image — only the changed files re-upload. The same blob is referenced by every manifest that includes it.
  3. Strong caching. The viewer sets ETag: "<sha256>" on every response, so browsers can cache aggressively and revalidate with If-None-Match (the Cloud Function returns 304 Not Modified instantly).

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Per-version manifests

Each version has a manifest file in Cloud Storage listing every file by literal path plus its hash + size + content type: 
{
  "version": 2,
  "title": "Q3 deck",
  "entryPath": "index.html",
  "files": [
    { "path": "index.html",      "sha256": "aa…", "size": 12034,  "contentType": "text/html; charset=utf-8" },
    { "path": "styles.css",      "sha256": "bb…", "size": 3120,   "contentType": "text/css; charset=utf-8" },
    { "path": "images/hero.jpg", "sha256": "cc…", "size": 824100, "contentType": "image/jpeg" }
  ],
  "createdAt": "2026-04-23T13:11:16Z",
  "createdBy": "<userId>"
}
When the viewer fetches /share/{presentationId}/images/hero.jpg, the backend resolves the current (or pinned) version’s manifest, looks up the literal path, reads the hash, and streams the blob. No HTML rewriting, no URL mangling — the author’s <img src="./images/hero.jpg"> goes straight through.

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Relative paths and the deck root

The deck root is whatever you passed to slideless push. Paths in HTML and CSS are resolved relative to the file they appear in:
  • ./foo.jpg from index.html → foo.jpg (deck root)
  • ../assets/foo.jpg from index.html → rejected (escapes the deck root)
  • /foo.jpg from anywhere → foo.jpg (root-absolute maps to deck root, not to /)
  • ./styles.css from subdir/page.html → subdir/styles.css
This matches how a static webserver resolves paths with the deck folder as document root. External URLs (https://..., //..., data:, blob:) pass through unchanged.

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Streaming and Range support

Large assets (video, big glTF models) are served with Accept-Ranges: bytes and support Range requests. <video> tags can seek correctly; clients can resume truncated downloads. The viewer caps each Range response at 50 MB to prevent memory spikes on the serving side.

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Size and file-count caps

See Presentations for the full plan-by-plan table. On the free tier: 50 MB per file, 250 MB total, 500 files max, 10 MB per HTML file.

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What doesn’t count against your quota

  • External CDN dependencies (https://unpkg.com/three@0.160/..., Google Fonts, any https:// URL).
  • Deduped assets on a subsequent slideless push — if an image is unchanged, it doesn’t re-upload and doesn’t re-charge storage.