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Command line#

uselayer calls the API with your key, so you can try Layer from a terminal before writing any code.

Every command says which Layer it's calling, ends with ✓ or ✗, and suggests the next command to run. When the API turns a request down, the reason and how to fix it are printed under the ✗.

Install#

You need Node 18.17 or later. Check with node -v; if it's missing or older, get it from nodejs.org.

There are two ways to run uselayer. Pick one:

Run with npx Install it once
Command npx uselayer login npm install -g uselayer, then uselayer login
What it does Downloads uselayer and runs it, without adding a uselayer command to your terminal. Installs it for your whole computer (-g means global), so uselayer works in any folder.
Good for Trying Layer, or a one-off check. Using it every day.
Every command starts with npx uselayer … uselayer …

With npx, keep typing npx uselayer each time: a bare uselayer gives command not found. The CLI knows how you started it, so the next command it suggests is always one you can paste as-is.

Check it's working with uselayer --version (or npx uselayer --version).

bash
npx uselayer login          # paste your key from the dashboard
npx uselayer matches --q nfl

If something goes wrong#

What you see Why Fix
zsh: command not found: uselayer (or bash: …) You ran it with npx, which doesn't install a command. Or it's installed globally, but npm's folder for global commands isn't on your PATH. Use npx uselayer …, or run npm install -g uselayer. If it's installed and still not found, run npm prefix -g, add the bin folder inside it to your PATH, then open a new terminal.
404 Not Found - GET https://registry.npmjs.org/uselayer. The package name was typed with something extra: here, a full stop at the end. Type exactly uselayer: npm install -g uselayer.
EACCES: permission denied during npm install -g npm's global folder belongs to another user on your computer. Use npx uselayer … instead, or install Node with a version manager such as nvm, which keeps global installs in your own folder. Avoid sudo npm install -g.
npm warn EBADENGINE Unsupported engine, or a SyntaxError when it starts Node is older than 18. Update Node, then run the command again.
  • Update: npm install -g uselayer@latest. npx can reuse a copy it downloaded earlier; npx uselayer@latest … makes it fetch the newest.
  • Uninstall: run uselayer logout first if you want your saved key removed too, then npm uninstall -g uselayer.

Your key#

uselayer login asks for your key from the dashboard, checks it with Layer, and saves it in ~/.config/uselayer/config.json, readable only by you. You can also pass it: uselayer login lyr_your_key, or echo $LAYER_KEY | uselayer login. uselayer logout forgets it.

If LAYER_KEY is set in your environment, it's used instead of the saved key, so scripts and CI don't need a login.

Commands#

Command What it does
uselayer matches [--q nfl] [--from 2026-10-03] [--to 2026-10-05] [--category sports] [--venue polymarket-us|polymarket] [--limit 50] [--offset 0] Live matches, soonest event first, as in GET /v0/matches: with Polymarket US, or polymarket.com with --venue polymarket. Each one shows both markets' ids and who checked the match.
uselayer match <market id> [--venue kalshi|polymarket|polymarket-us] [--with polymarket] The same market on the other venue, as in GET /v0/match, with both venue links. Leave --venue out and it's read from the id: an upper-case ticker is Kalshi, a :long or :short side is Polymarket US, and anything else is polymarket.com. A Kalshi market's twin is looked up on Polymarket US; --with polymarket looks on polymarket.com. When there's no twin, it says why.
uselayer profit --match KXFEDDECISION-26OCT-C25 --contracts 100 --kalshi 0.42 --polymarket 0.55 Buy one side on Kalshi and the other on Polymarket at these prices: the profit after both venues' fees, as in POST /v0/profit. --match is the match's Kalshi ticker: Layer fills in both markets' fees and how long your money is held, and says which it filled in. Use --polymarket-us 0.55 for Polymarket US instead. The check runs on Layer from the prices you give it; Layer doesn't fetch venue prices for you.
uselayer login [key], uselayer logout Save or forget your key.
uselayer help All of the above. Add --help to any command for its options.

profit options#

Option Meaning
--contracts Contracts bought on each venue.
--kalshi, --polymarket, --polymarket-us The price you pay on each venue, in dollars (0.42 is 42¢). Send --kalshi and one of the other two.
--match The Kalshi ticker of a live match. Layer fills in every fee and --days you leave out; anything you pass yourself is used instead.
--category or --fee-rate Polymarket's fee: the category's default rate, or the market's own feeSchedule.rate. One is needed with --polymarket unless you send --match. --exponent sets feeSchedule.exponent.
--fee-coefficient Polymarket US's fee (0.0695 by default).
--fee-multiplier, --fee-type The Kalshi series' fee_multiplier and fee_type.
--kalshi-role, --poly-role maker if your order rests on the book first (taker by default).
--settles-at 2026-10-04 or --days 4 When the money comes back; adds return per day.

For scripts#

Add --json to any command and it prints only the API's JSON answer, the same as calling the API directly. A failed call prints the API's error JSON and exits with status 1.

bash
uselayer matches --q nfl --json | jq -r '.matches[].kalshi.market_id'

--local calls a Layer running on http://localhost:3100 instead of https://uselayer.sh; LAYER_API_URL points it anywhere else.