- Spread vs baselineWatches
- Events ·
thinningSignals - Poll or WebSocketFeeds
- You do, not the toolActs
A spread that suddenly widens is the order book raising its hand. Market makers pull back when they sense risk, an event landing, informed flow arriving, liquidity draining, and the spread blows out before the price has finished moving. A spread-widening watch turns that into a signal you can act on. This is a monitor, not a trader: it tells you when to look, and the decision stays yours.
Be clear about what this is up front. Resolved Markets is, at its core, a historical order-book archive, it captures Polymarket’s book as snapshots and stores the history; the live orderbook endpoint and WebSocket are a convenience layer on top, returning the current book for active markets. A spread-widening watch leans on that live layer, but it is still a read-only notifier: it detects the condition and pings you, it does not place orders. What you do next is your call, made in your own venue. The honesty matters, because a monitor that promised to trade for you would be lying about the product.
Why spread widening is worth watching
An event landing
Makers widen ahead of and into scheduled events, so a spread blow-out is often the first sign something is repricing.
- Pre-event caution
- Repricing underway
- Earlier than the mid
Liquidity thinning
A wider spread usually rides alongside draining depth, fewer resting orders, a more fragile top of book.
- Depth draining
- Fragile touch
- Risk rising
A relative signal
Absolute spread says little across markets; the alert fires on a market widening relative to its own normal.
- Own baseline
- Comparable across markets
- Not an absolute number
Poll the endpoint or stream the socket
There are two ways to feed the watch, and the right one depends on how fresh you need it. Polling the live orderbook endpoint is simple and works on any tier, you ask for the current book on a schedule and compare. The WebSocket pushes the live book roughly every one to two seconds with no polling loop, but it is a paid-tier feature.
- spreadThe field the watch compares each tick
best_bidbest_askThe touch the spread is measured across- poll /
orderbookSimple, any tier, your chosen cadence - WebSocket ~1-2sPushed live, paid tiers only
- Polling is the easy start, request the live book on an interval, read the spread, compare to baseline; every tier spends a credit per request (a live orderbook read is 1 credit), with the free tier drawing from its 5,000-credit monthly allowance.
- The WebSocket removes the loop, it pushes the book every one to two seconds, so the watch reacts as the book changes rather than on your timer, with connection counts that rise by tier.
- Either way you are reading the same spread field; the choice is freshness and effort, not a different signal.
- For a slower-moving category, a gentle poll is plenty; for fast crypto markets near an event, the push feed earns its keep.
Threshold against the market’s own baseline
A fixed spread threshold fires constantly on naturally wide markets and never on tight ones. The fix is to measure each market against itself: establish a quiet-period baseline spread, then alert when the current spread runs some multiple above it. That makes a thin overnight market and a deep daytime one comparable, because each is judged on its own normal.
- 1Resolve the markets you want to watch to their conditionIds, and pick your feed, poll or WebSocket.
- 2Build a rolling baseline spread per market from its recent quiet periods, not a single global number.
- 3Fire an alert when the live spread exceeds the baseline by your chosen multiple, and require it to persist a beat so one noisy tick does not trip it.
- 4Send the notification, your channel of choice, with the market, the current spread, and how far above baseline it ran.
It tells you to look, you decide
This watch detects a condition and notifies you. It does not and cannot place a trade, Resolved Markets reads the book, it never touches an order. Treat the alert as a prompt to investigate in your own venue, not as an instruction the system carries out. A monitor that respects that line is one you can actually trust.
One more honest note on the signal itself: the spread is built from resting quotes, an intent to trade, not a record of executed volume. A wide spread tells you makers have stepped back; it does not tell you a trade happened. Read it as the warning it is, and confirm with depth and the price path before you conclude anything.
A widening spread is the book flinching. The watch catches the flinch and hands it to you, what you make of it is the part no data feed should pretend to decide.
Build your watch
The docs cover the live orderbook endpoint and the WebSocket feed; the crypto page shows which markets you can monitor.
Frequently asked questions
Why monitor spread widening at all?
Because makers widen when they sense risk, an event landing, informed flow, liquidity draining, and the spread often blows out before the price has finished moving. A widening spread is an early flag that something is repricing or that the book is thinning, which makes it a useful condition to watch.
Should I poll the orderbook endpoint or use the WebSocket?
Polling the live orderbook endpoint is simple and works on any tier, you request the book on a schedule and compare the spread. The WebSocket pushes the live book roughly every one to two seconds without a polling loop, but it is a paid-tier feature with connection counts that rise by tier. Both read the same spread field; the difference is freshness and effort.
How do I set a threshold that works across markets?
Measure each market against its own baseline rather than a fixed number. Build a quiet-period baseline spread per market and alert when the current spread runs some multiple above it, requiring it to persist a beat so a single noisy tick does not fire. That makes a naturally wide market and a tight one comparable, because each is judged on its own normal.
Can the watch place a trade when it fires?
No. Resolved Markets is a read-only data platform, it captures the order book and never places orders. A spread-widening watch is a monitor that detects the condition and notifies you; acting on it happens in your own venue and is entirely your decision. Treat the alert as a prompt to look, not an instruction the system carries out.