Tab Share link shortener

A tiny, self-hostable shortener for Tab Share links -- the ones that carry a whole tab collection in the URL #fragment and can run to several kilobytes.

Part of the Tab Share suite: the companion to the Tab Share browser extension (Chrome Web Store), which packs a group of tabs into one link that opens in any browser with no extension. This service shortens that link -- and because it just redirects to the viewer, the short URL opens the same way, no extension either. (The extension links here from Options -> Shorten links, where Tab Share shortener is the recommended provider.)

• Any length. A 40-page collection is ~4 KB; a 100-page encrypted one ~6 KB. This service takes it (POST body, or a large GET) where TinyURL / is.gd choke.
• Two code styles.
  • code -- short and random: s.example.com/k7Rm2pq
  • words -- readable, Twitch-clip style: s.example.com/swift-amber-otter
• No account, aggregate-only stats. By day: per-link hit counts, the referring host of each click, and the visitor's browser family + major version -- no IP, no geolocation, no full User-Agent, no cookies, no third-party trackers, never sold. See PRIVACY.md; turn it all off with SHORTENER_ANALYTICS=0. Identical links are de-duplicated.
• Optional admin panel at /admin (token-gated, off by default): link table (target host only; a destination is revealed one link at a time), revoke / bulk revoke or delete by filter, manual/vanity links, host-allowlist editor, the analytics above, an on-request histogram of the domains people bundle (reddit.com, never the post), and a Prometheus /admin/metrics endpoint. See SELF-HOSTING.md.
• Not an open redirector. It only shortens links pointing at a host on its allowlist (your Tab Share viewer), which is what keeps it off the phishing radar.
• No npm dependencies. Plain Node 20+ (24+ for the SQLite backend). Storage is a JSON file or node:sqlite, both built in. Vendors two files in src/lib/ -- lz-string (MIT) and the Tab Share share-codec (AGPL-3.0, same project) -- used to decode a link's bundled-page domains for the admin histogram. A Cloudflare Worker port and Linux / Windows installers are in deploy/.

Licensed AGPL-3.0-only (it's a network service -- same terms as Tab Share).

Run it locally

npm test          # store + Node server + Worker checks, no network
npm run dev       # http://localhost:8779, accepts localhost:8777 + kaikayy.github.io targets
npm run gen:worker  # regenerate deploy/worker-words.js after editing src/words.mjs

# shorten something
curl -X POST localhost:8779/api/shorten \
  -H 'content-type: application/json' \
  -d '{"url":"https://kaikayy.github.io/multi-link-share/#NoZg...","mode":"words"}'
# -> {"code":"swift-amber-otter","shortUrl":"http://localhost:8779/swift-amber-otter",...}

Wire it into the extension

Tab Share ships a built-in Tab Share shortener provider (Options -> Shorten links) with a Normal / Readable words toggle. It's pre-filled with the first-party public instance at https://s.kaikay.de, which allow-lists the built-in viewer -- so the default setup needs no configuration. Off until you turn it on; still opt-in per link.

The public s.kaikay.de instance currently shortens links pointing at kaikayy.github.io only (the built-in viewer). If you run your own viewer, self-host the shortener too (below), or open an issue to have your host added to the public instance's allowlist.

To point it at your own instance, put its address in that same field. For a local dev instance: npm run dev here, then set the address to http://localhost:8779 in a DEV_LOCALHOST=1 extension build.

Native contract: GET <address>/new?url=<enc> (add &mode=words) -> the short URL as plain text.

How it compares

What each shortener keeps when someone opens a short link:

Shortener	Logged on each click	Cookies / 3rd-party trackers	Data sold or shared
this one (s.kaikay.de or self-hosted)	aggregate day counts only: hits, referrer host, browser family + major version. No IP, no geolocation, no full User-Agent, no per-visitor row.	none	never
da.gd (built into the extension)	a hit counter; small open-source service, no ad or analytics scripts	none observed	no
TinyURL (built into the extension)	IP address, browser type + version, referring URLs, timestamps; forwards your full referrer to the destination	yes	not stated in its policy
Bitly (not offered)	per click: timestamp, IP, user-agent, country, city, device, browser, referring domain	yes	yes -- selling click analytics is a paid feature

TinyURL / Bitly rows are summarised from their published policies and independent testing as of 2026 and can change. Full detail for this one is in PRIVACY.md.

API

Route
POST /api/shorten	{ url, mode?, ttlDays? }	201 { code, shortUrl, mode, expires, keepToken }
POST /api/keep	{ code, keepToken, ttlDays? }	200 { code, expires } -- pin a link (or re-set its TTL)
GET /new?url=<enc>&mode=	compat shim	200 text/plain short URL; keep token in the X-Keep-Token header
GET /:code		302 to the target (HTML meta-refresh if the target is very long)
GET /api/health		200 { ok, store, allowedHosts, ... }
/admin, /admin/api/*	Bearer / cookie token	panel + JSON API (incl. POST /admin/api/links/bulk); 404 when SHORTENER_ADMIN_TOKEN is unset
GET /admin/metrics	Bearer / cookie token	Prometheus text exposition

How long a short link lives. By default a new short code stops resolving 30 days after it was created (SHORTENER_TTL_DAYS). The full share link the caller also copied is never affected -- only the short code is forgotten. To keep one for good, POST /api/keep with the keepToken you got back at creation (ttlDays: 0 pins it; a positive ttlDays sets a fresh window). An operator can also pin or expire any link from the admin panel. Set SHORTENER_TTL_DAYS=0 to make links never expire by default. Links created before this default existed (shortener < 0.3.0, or while SHORTENER_TTL_DAYS was 0) carry no expiry and keep resolving -- the TTL is stamped once, when the link is made.

See CONTRACT.md for the exact rules a response/redirect must follow, and SELF-HOSTING.md to deploy.

Configuration

Every knob is an env var -- full list and defaults in src/config.mjs. The ones you'll actually set:

Env	Default
SHORTENER_BASE	http://localhost:8779	public origin, no trailing slash
SHORTENER_HOSTS	kaikayy.github.io	comma list of allowed target hosts (empty = open mode)
SHORTENER_HOSTS_FILE	--	newline-delimited host file, merged with SHORTENER_HOSTS; re-read on SIGHUP
SHORTENER_LOG	off	1 or a dir: log redirects (truncated IP) to per-day files
SHORTENER_PORT / SHORTENER_HOST	8779 / 127.0.0.1	bind address
SHORTENER_STORE	data/links.json	store file path
SHORTENER_STORE_BACKEND	infer from path	file or sqlite (Node 24+)
SHORTENER_TTL_DAYS	30	default link lifetime in days (0 = forever); per-link override via ttlDays / POST /api/keep
SHORTENER_RATE	30	creates per IP per minute (0 = off)
SHORTENER_TRUST_PROXY	off	set 1 behind a reverse proxy to read X-Forwarded-For
SHORTENER_ADMIN_TOKEN	off	set a long random string to enable /admin; unset = the tree 404s
SHORTENER_ANALYTICS	1	0 disables redirect analytics; SHORTENER_ANALYTICS_DAYS sets retention (365)

Contributing

Bugs -> an issue. Questions and ideas -> Discussions. See CONTRIBUTING.md. Version history in CHANGELOG.md.

Security

Found a vulnerability? See SECURITY.md -- please report it privately, not as a public issue.

Support

If this project is useful to you, you can support development on Ko-fi: