Predxy

What it is

A free web index of prediction-market questions. Each row is a cluster — one question with every venue that carries it combined into one probability — and the home page ranks the clusters by the sum of 24-hour volume across those venues. The about page says nobody can pay for a place, and that the one page people edit, Today, labels every pick. On 27 October 2026 the header counted 388,282 questions across 15 venues, 1,380 resolving that day, 1.83 billion USD of open interest (which the site calls market cap) and 199.9 million USD of 24-hour volume.

What the site gives a reader, with no account:

• Top 100 and the browse pages, ordered by weight, by the largest 24-hour move, by the share of lifetime volume that arrived today, by the soonest to settle or by the widest disagreement between venues. A separate page lists price gaps between venues.
• A question page with the combined probability, a probability history chart since recording began, every venue carrying the question with its own price and a link to its own resolution rules, and a table of what a stake at each venue pays before fees.
• Today, an edited front page. Editors may pick the lead and the stories from the index, with research the about page says is assisted by AI; every pick is labelled, and the rest of the page follows the index's arithmetic, which the page prints.
• Venues, a ranking on a weighted composite with the per-metric breakdown published, plus each venue's sync freshness, indexed-to-open market coverage and the countries it refuses.
• A Fear & Greed score for the whole market, which the site's own note calls a heuristic and "not a forecast".

The API that feeds all of this is sold separately (below) and is the reason this card also sits in the data-API listing.

The operator is not named. The footer reads "© 2026 PREDXY", the terms (published 20 September 2026) and the credits page name no company, country or address, support is contact@predxy.com, and the GitHub organisation the footer links to had no public repository on 27 October 2026. The about page spells the name out to distinguish it from Predyx, a Bitcoin prediction market, and Predix, GE's industrial software.

Availability

Reading needs nothing. An account, which adds a watchlist and a "For you" shelf, requires you to be 18. The terms name no restricted country and no identity check, and say only "use Predxy only where lawful".

The job here is reading, so the venues' reach does not apply to this card: a US reader can read every cluster, including those priced only on Polymarket's international exchange. What the venue restrictions govern is the trade button. The site keeps two lists per venue — countries the venue refuses to serve, and countries whose own regulator prohibits the venue and may penalise the individual — and hides the button on either, with a warning on the second. The decision is made in your browser from the country you set, so the same page is served to everyone, and a question page viewed from Türkiye on 27 October 2026 read "Polymarket US does not serve customers in Türkiye". On the venues page that day Polymarket refused 40 countries and was prohibited in 11, Kalshi 47 and 4; nine of the fifteen venues carried "none known — research incomplete for some venues" in the prohibited column. The terms add that "a visible link is not a statement that you may trade there".

Read from the terms, the about page and the venues page on 27 October 2026.

Pricing

The site is free, with no plan behind it. What is sold is the API:

• Free — 0 USD. 100 requests a minute. Approved by hand by the operator; the developers page says to sign in to request access.
• Pro — 39 USD a month. 300 requests a minute. Starts as soon as the payment settles.
• Pro Max — 59 USD a month. 1,000 requests a minute.

All three list the same three things — market data and probabilities, venue market details, recorded price history — so the plans differ in rate alone. The allowance is counted per account across both of an account's keys, and the docs say there is no daily or monthly quota. No annual price is published, and a /pricing URL returned 404; the plans live on /developers.

Predxy places no order and takes no cut, so the fee fields are null. Two other revenue lines are disclosed: the terms say "some outbound venue links may include referral identifiers and may generate compensation for Predxy", and the home page carries a "featured on" badge whose link carries a referral parameter of its own.

Read from the developers page, the documentation and the terms on 27 October 2026.

Markets & resolution

Whatever the fifteen venues list that the matcher can cluster, across politics, sport, macro, crypto, technology, science and culture. Scalar markets are excluded from the index, as are questions that settle within 48 hours or have reached a price of 99 or 1. Predxy resolves and settles nothing.

The matching claim is narrower than an aggregator's usually is, and the about page is careful about it: "a cluster asserts that its markets are comparable, not the same." Resolution rules differ between venues in settlement date, source of truth and edge cases, so every question page shows each venue's own rules beside its price, and the page's "where this question trades" block says so in as many words. How the matching is done is published only to this extent — "measured, reviewed by a person when uncertain, and never done by similarity alone" — with no score, no method and no match list a reader could audit.

Two venues on one row is less common than the headline suggests. Today's lead question on 27 October 2026 — League to Win World Series: American League — was "1 venue, 1 priced", on Polymarket US, and the combined figure is then that venue's price. The venues page shows why: Polymarket and Kalshi together carried about 146 million USD of the day's 199.9 million USD of volume, so a volume-weighted number on a question both carry is largely whichever of the two is busier on it. The venue's own rules are still the thing to read: the settlement source and why the same contract costs two prices cover what the single number leaves out.

A venue's price is marked stale after more than two minutes behind and drops out of the combined price after fifteen; a venue that cannot be placed on the question's side is left out of the price but still counted in the venue and volume totals.

Integrations

A read-only JSON API over HTTPS at api.predxy.com, with a staging host and an identity host that issues tokens. Authentication is OAuth 2.0 client credentials: a POST to the token endpoint with a client id and secret returns a token valid for 900 seconds, with no refresh token, under the scopes predxy.api.read, predxy.api.detail and predxy.api.history. The API sends no CORS headers, so it is called from a server, not a browser. An unauthenticated request to /v1/index answered 401 on 27 October 2026.

The OpenAPI document (version 1.0.0) lists twenty paths: the index, its search, its countries, its gaps and per-cluster history; markets, a market's detail, history, comments and engagement, and stats; a change feed for keeping a copy current; a resolution calendar; venues, their ranking and history; and the Fear & Greed score with its history. History takes a window (default 7d) and an interval (default 1h); older than 90 days is one close a day. Rate-limit state comes back in RateLimit-Limit, RateLimit-Remaining and RateLimit-Reset, and a 429 carries Retry-After.

There is no SDK, no WebSocket, no MCP server and no CSV or JSON download from the site; the change feed is the offered route to a local copy. Matching a question across venues is the procedure for checking a cluster yourself, and PMXT is one client that reaches several of the same venues directly.

Limitations

One number hides which venue made it. The combined probability is volume-weighted, and on most days two venues carry most of the volume. Where a question trades on one venue the "index" figure is that venue's last price, and the row does not say so until you open it.

Coverage is partial where it matters most. On 27 October 2026 the venues page reported 105,701 of Polymarket's 275,632 open markets indexed and 62 of Outcome's 196; Kalshi, Myriad, Pascal, Skew and Hyperliquid were complete. Limitless, Opinion, Predict.fun and SX Bet showed no market-cap or volume figure at all. The docs say some venues' prices appear only with the venue's permission.

The matching is not auditable from outside. "Reviewed by a person when uncertain" is the whole published method; there is no confidence score and no exported list of pairs.

History starts on 27 August 2026, and a dash in a change column means not enough history, not no movement.

The country lists are admitted to be unfinished. Nine of fifteen venues carried "research incomplete for some venues" under regulator prohibitions, so a visible trade button is not a finding that you may trade.

No alerts, no export, no app. The watchlist is a page, not a notification; nothing pushes. The only email the site sends is an announcements list.

The operator is unnamed, and the terms carry no governing law. The AI-assisted summaries, the terms say, "may contain errors", and the Fear & Greed score is a heuristic the site itself says is not validated sentiment.

Alternatives

For the price gap rather than the combined number, CrossOdds matches Kalshi and Polymarket with a published confidence score and an API at 20 USD a month, and ArbiTrack adds PredictIt. For the same two venues in one schema with history, Oddpool. For a venue ranking and reference rates rather than a question index, Adjacent. To build the clustering yourself, PMXT is a CCXT-shaped client over several of these venues and matching a question across venues is the procedure.