How to plant a tripwire inside the self-hosted apps you already run. Every recipe assumes you have a Mantis instance running and a key minted (mantis new "memo"). The URL referenced below is the per-key trigger URL printed by mantis new. Three flavours of recipe:
  1. Drop-a-file — generate an artifact with mantis new --<fmt> or mantis download <id> --<fmt> and upload it. The app stores the bytes; later, when anyone views/opens the file, an embedded reference fetches the trigger URL.
  2. Paste-a-URL — no new artifact needed. You put the trigger URL into a field the app will hit on your behalf (a credential, a webhook, a dashboard tile, etc.).
  3. Platform artifact — Wallet and NFC artifacts depend on the platform action: a pass install/fetch/remove, or a phone scan/tap.

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Photo libraries — Immich, PhotoPrism, Lychee, LibrePhotos

Upload vacation.svg to your photo library. Caveats per app:
  • Immich: SVG uploads land in the library, but Immich generates a server-side raster thumbnail by default — the thumbnail does not fire. Opening the original (link or “Open original”) fires every time. Useful for detecting download-and-view, not gallery scrolling.
  • PhotoPrism / Lychee: similar — SVG previews depend on the app’s preview pipeline; verify with mantis hits <id> after a single render.
For a passive scraper signal (much weaker) you can also place a JPEG whose EXIF UserComment contains the trigger URL; this only fires if someone runs exiftool on the file.

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Document management — Paperless-ngx, Mayan EDMS

Upload q4.pdf to Paperless. Paperless OCRs the document but does not auto-fire the canary during indexing. When you (or anyone) clicks the document in the UI to preview it, the browser PDF viewer hits the trigger URL on open. The clickable URL annotation and /OpenAction both fire. EML is useful for email-archive workflows. Paperless can ingest .eml; opening the message preview fires the inline <img>.

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Notes — Joplin, Trilium, Logseq, Obsidian sync

Import the Markdown file as a new note. The first time the note opens (or every time, depending on the renderer), the inline image renders and fires. Trilium and Logseq render Markdown server-side or on-render — both work. Obsidian renders Markdown in the desktop client; the inline image fires from your editor when the note is opened.

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Calendar — Radicale, Nextcloud Calendar, DAViCal

Import event.ics into your calendar app. Apple Calendar and macOS Calendar fetch attachments with FMTTYPE=image/* on open; behavior varies for other clients. The URL property is also clickable from the event detail.

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Contacts — Radicale, Nextcloud Contacts, CardDAV

Import the vCard. CardDAV clients (macOS Contacts, iOS Contacts, Thunderbird Address Book) fetch the PHOTO;VALUE=URI reference on contact render. The URL field is also surfaced as the contact’s URL property.

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Password vaults — Vaultwarden, Bitwarden, Padloc

No new artifact needed. Create a login entry:
  • Name: Internal admin — DO NOT TOUCH
  • URL: paste your Mantis trigger URL (e.g. https://mantis.example.com/c/abc123)
  • Username: admin
  • Password: anything random
Bitwarden’s “Launch & autofill” hits the URL. The browser extension’s icon-click also fires. Manual reveal does not fire — only when the URL is followed.

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Dashboards — Heimdall, Homer, Homepage, Dashy

No new artifact needed. Add a tile:
  • Label: Internal Wiki / Admin Console / Backup Portal
  • URL: trigger URL
If anyone clicks the tile, the canary fires. Doubles as a phishing-resistance training tool for housemates.

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Bookmarks — Linkding, Wallabag, Hoarder, Karakeep, Shiori

No new artifact needed. Paste the trigger URL as a bookmark. Most of these services scrape the URL on add to extract metadata, so the canary fires immediately on save (one expected hit). Re-fetches or re-syncs also fire — this signal is noisy. Best for detecting force-rescan attacks rather than per-view activity.

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Home automation — Home Assistant, n8n, Node-RED

No new artifact needed. Add a webhook integration / node:
  • URL: trigger URL
  • Wire it into an automation that should never run (e.g., guarded behind a condition that’s always false).
A misconfiguration, manual test, or attacker-modified config will fire the canary.

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Code hosting — Gitea, Forgejo, Gogs

Drop the generated README.md into a fresh private repo. Anyone with read access loads the README and fires the canary. Useful for detecting unauthorised clone-and-browse. For a separate vector inside the same repo, you can also add a fake .env whose first line is the trigger URL. Exfiltrators scanning for secrets often follow URLs in .env files.

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RSS / social — FreshRSS, Miniflux, Mastodon, Pixelfed

No new artifact needed. Publish a status or feed item containing the trigger URL. Federating instances and aggregators fetch OpenGraph metadata from the URL → the canary fires every scrape. This is a federation/scraper detector, not a user-clicked detector.

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Cloud storage — Nextcloud, Seafile, OwnCloud

Any of the artifacts above work — drop into a folder and grant a share link. The recipe is the same as the file-format’s intended consumer: the .pdf fires when previewed in the browser’s PDF viewer; the .eml fires when previewed in Nextcloud Mail; the .vcf fires when imported into Contacts; etc. For a single-file high-fidelity option, use mantis new "Confidential" --folder /tmp/honey.zip — the unzipped folder contains a coordinated set of bait files that all fire the same key.

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Mail servers — Mailcow, Mail-in-a-Box, Stalwart

Place the .eml into an archive or junk folder. Any mail client opening the message renders the HTML body and fires.

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Verification

After dropping a recipe, confirm it landed:
The hit’s user_agent field tells you which renderer fired (browser? mail client? CalDAV?), useful for narrowing down where the access happened. For broader coverage, set the key’s monitor mode to latch so the next view trips an Uptime Kuma alert:
See the Uptime Kuma section of the main README for the rest of that flow.

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Edge compatibility

Mantis has two URL-emitting modes: Every artifact below is a URL container, but Wallet has one server-backed-only advantage: Apple Wallet web-service callbacks need the stateful server to record install/uninstall/fetch events. Pick the mode first, get a URL, then drop it into the format.

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Compatibility matrix

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Trade-offs

Use server-backed when you want:
  • A hit log you can query (mantis hits, dashboard, /api/keys/<id>/hits)
  • Uptime Kuma monitor mode (latch/window)
  • Webhook retry queue + delivery state on each hit
  • Compact URLs (small QR codes, clean-looking VCF/ICS, fitting in tight UI fields)
Use mantis-edge when you want:
  • Zero server attack surface (no DB, no API, no auth to compromise)
  • Sub-50ms response from Cloudflare’s edge globally
  • A canary that survives even if your main mantis server is down
  • One-shot fire-and-forget: you don’t care to query past hits, just want a webhook on access
Combine them by minting two URLs (one of each) for the same artifact — e.g. mantis new "Q4" --pdf q4.pdf plus a separately-minted edge URL pasted into the PDF body — and you get both a live audit trail and a degradation-proof tripwire.

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Format standards reference

Every artifact Mantis generates follows a published spec, so any compliant consumer renders it correctly:

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Why this matters for self-hosted apps

App ecosystems treat their input formats as black boxes that conform to a spec. Immich doesn’t know your SVG was generated by Mantis — it just sees a W3C-conformant SVG with an <image href>. Paperless doesn’t know your PDF embeds a tripwire — it sees an ISO 32000 PDF with an OpenAction. The standards layer is what makes a Mantis canary indistinguishable from a “real” file at the format level. The only fingerprint is the URL itself. For maximum stealth:
  • Use a custom domain for your server (assets.your-company.com/c/<id> looks innocuous; mantis.example.com/c/<id> does not)
  • Or use mantis-edge with a domain like cdn.your-company.com — the URL still reveals the path /c/<blob>, but the host stays neutral
  • The MANTIS_PUBLIC_PATH env var (default /c) lets server-backed mode use stealthier paths like /img, /track, /r