# Metaculus

Proper scoring and public track records on questions nobody can take a position in.

*https://predictionmarkets.tools/tools/metaculus · Forecasting Platforms*

## Facts

### At a glance

| Field | Value |
| --- | --- |
| Vendor | Metaculus |
| Category | Forecasting Platforms |
| Job | forecasting |
| Website | https://www.metaculus.com |
| Pricing model | free |
| Free tier | true |
| Open source | true |
| Licence | BSD-2-Clause |
| Self-hosted | true |
| Tested hands-on | false |
| Last updated | 2026-09-19 |

### Availability

| Field | Value |
| --- | --- |
| Jurisdictions | global |
| Open to US persons | true |
| KYC required | false |

### Markets

| Field | Value |
| --- | --- |
| Subjects | politics, macro, science, business |
| Settlement | play_money |
| Resolved by | Metaculus staff resolve each question against the source named in its own resolution criteria, and annul it when that criterion cannot be evaluated. |

### Economics

| Field | Value |
| --- | --- |
| Taker fee | none |
| Maker fee | none |
| Liquidity model | none |
| Platforms | web |
| AI features | none |

### Interfaces

| Field | Value |
| --- | --- |
| API | true |
| WebSocket | false |
| Scripting | none |
| Python | false |
| MCP server | false |
| Export | api |

### Capabilities

Yes: charting, automation, calibration_scoring, alerts

No: screening, order_book, backtesting, live_trading, paper_trading, portfolio_tracking, cross_venue, news, tax_reporting

*Verified: pricing 2026-09-19; availability 2026-09-19; markets 2026-09-19; capabilities 2026-09-19.*

## What it is

A question site with a scoring system attached, run by Metaculus, Inc. You read a question, you
enter a probability, and at resolution you are scored against a proper scoring rule. There is no
balance, no position and nothing to sell before close — the only thing you accumulate is a record.

The scoring is the product, and Metaculus documents it in more detail than most vendors document
their pricing. Everything is built on the log score, which is proper: the way to maximise it on
average is to state the probability you actually believe. Because a raw log score is always
negative on a binary question and reads badly, two rescalings sit on top of it. The **Baseline
score** compares a forecast to a fixed chance benchmark and is positive when you beat chance — on
resolved binary questions the median observed Baseline score is about +17. The **Peer score**
compares a forecast to every other forecast on the same question; the sum of all participants'
Peer scores on a question is always zero, which makes it the harsher and more informative of the
two. A **spot** version of either ignores how long the forecast stood and reads only the value at
one moment, usually when the Community Prediction is revealed.

Scores are time-averaged over the life of a question, so a forecast left standing counts for every
day it stood. That is the mechanical reason the site rewards updating and not simply arriving late
with the answer.

The Community Prediction is a time-weighted median of forecasters, and it scores better than most
of the people feeding it — its own Peer score is positive by construction.

## Availability

Open worldwide, free, no identity check. The terms of use state that the service is offered to
individuals aged 13 and over, that Metaculus operates it in the United States, and that it makes
no representation that the service is appropriate for use elsewhere — a reader outside the US is
told they are responsible for their own local law. There is no money involved on the forecasting
side, which is why none of the jurisdiction machinery that governs an event exchange applies here.

Tournament prizes are a separate matter: they are paid out, and payment mechanics and eligibility
are handled per tournament rather than by a blanket rule on the site.

## Pricing

Free to forecast on, and free to read. Metaculus earns from organisations rather than from
forecasters — tournaments commissioned by a partner, private instances of the platform deployed
inside an organisation, engagements with its Pro Forecasters, and workshops. None of that is
something a reader of this card buys.

The one number a forecaster sees is a tournament prize pool. These are public and vary widely; on
19 September 2026 the tournaments index showed pools from none at all up to $50,000 for the bot
tournament, with several in the $3,000 to $15,000 range. Your share is proportional to the square
of your sum of Peer scores, each one weighted by its question's weight in the tournament. A
negative sum pays nothing, and in tournaments ending after 1 June 2025 a share that works out
below $50 is not paid at all — that money goes to the forecasters above you. The coverage term
that older descriptions still quote belongs to the scheme this one superseded in March 2024.

## Markets & resolution

Questions are written by staff and by the community, grouped into tournaments and question series.
Subject matter skews to what research funders care about — infectious disease burden, AI capability
and policy, geopolitics, energy and climate, macro indicators, space — rather than to whatever has
an order book somewhere.

Resolution is by Metaculus against the criteria published on the question, and the interesting case
is the one no venue has an equivalent for: a question whose criterion turns out not to be
evaluable is **annulled** rather than forced to an answer, and annulled questions do not score.
That is cheap to do when nobody holds a position, and it is one of the real differences between
this and a venue, where a resolution has to land somewhere because money is sitting on it.

Some questions are collaborations with named institutions, and Metaculus says so on the tournament
page. The Respiratory Outlook 2025/26 is described on its own page as a collaboration with the US
Centers for Disease Control and Prevention, with the note that community forecasts are shared with
the CDC and do not necessarily reflect CDC views. The Horizon Scanning Tournament is described as
part of a study group run with Renaissance Philanthropy and the UK's Advanced Research and
Invention Agency. Those are the two partner claims that check out against Metaculus's own pages; a
great deal else gets asserted about Metaculus's institutional users in places that are not
Metaculus.

## Integrations

The API is the thing to check before planning anything, because it changed. Every request now
requires an account token in an `Authorization` header — an unauthenticated call is rejected with
a message saying so. With an ordinary account you get your own data, open question text, the text
and resolution of closed questions you predicted on, staff comments, and the current Community
Prediction on roughly 50 questions. On everything else, aggregation data is simply absent from the
response. A separate tier for bot developers widens that to around 250 open and 250 resolved
questions, by application. Commercial use requires a written agreement, and the terms of use
prohibit using the data to train or evaluate machine-learning models without written permission.

The platform code is open source under BSD-2-Clause and actively committed to — the repository was
last pushed to on 18 September 2026 — and the API documentation notes that the access restrictions
above do not apply to a custom instance you run yourself. Metaculus also sells hosted private
instances as a service.

There is no first-party Python client. The `metaculus` package on PyPI is not Metaculus's: it is
version 0.0.2, last uploaded in February 2019, published by an unrelated author and pointing at a
GitLab repository. Installing it will not error, and it is not the vendor's.

## Limitations

The API restriction is the limitation that matters, and it is recent enough that most third-party
descriptions of Metaculus are wrong about it. If your plan was to pull the Community Prediction
across thousands of questions for analysis, that is now an application rather than a GET.

There is nothing to arbitrage against, by design. A number on Metaculus cannot be traded anywhere,
so the usual argument that money keeps a probability honest does not apply — what keeps it honest
is a proper score and a public record, which works on people who care about the record and not at
all on people who do not.

The accuracy record is a leaderboard about forecasters, not a claim about the aggregate being
right in any particular case. And the empirical score figures Metaculus publishes for Baseline and
Peer are marked as of November 2023, so the benchmarks you compare your own score against are
three years old.

## Alternatives

[Good Judgment Open](https://predictionmarkets.tools/tools/good-judgment-open) is the same job with a different scoring rule —
Brier rather than log — and a commercial firm on the other end of it recruiting from the
leaderboard. [Manifold](https://predictionmarkets.tools/tools/manifold) is the opposite trade: many more questions, far faster,
resolved by whoever wrote them, and scored by profit in a play currency rather than by a proper
scoring rule.

## FAQ

### Is the Metaculus API free and open?

It is free but no longer open. As of September 2026 every request needs an account token, and aggregate values such as the Community Prediction are returned on only about 50 questions. Wider access for bot developers and any commercial use go through a request form.

### Can you win money on Metaculus?

Only through tournaments. Nothing is traded and there is no balance to deposit or withdraw; a tournament divides a fixed prize pool among forecasters in proportion to their squared sum of Peer scores, and a negative sum pays nothing.

### What is the difference between the Baseline score and the Peer score?

Both are rescalings of the log score. Baseline compares you to a fixed chance benchmark, so it can be positive for everyone on an easy question. Peer compares you to everyone else on the same question, and by construction all participants' Peer scores sum to zero.

## Background

- [Scientific and government forecast hubs](https://predictionmarkets.tools/guides/scientific-forecast-hubs.md) — Public-health agencies run open, scored forecast hubs anyone can join. The unit of submission is a model, not a person, and nothing there is a personal record.
- [What a forecasting platform's score actually measures](https://predictionmarkets.tools/guides/what-a-forecasting-score-measures.md) — Proper rules, the two Brier conventions that differ by a factor of two, crowd-relative scores that do not travel between sites, and why profit is not accuracy.
- [How accurate a prediction market's price actually is](https://predictionmarkets.tools/guides/how-accurate-the-price-is.md) — What research establishes about reading 73 cents as a 73% chance — where market prices are calibrated, the deviations that recur, and what the horizon does.

## Also worth comparing

- [Manifold](https://predictionmarkets.tools/tools/manifold.md) — Anyone can open a question, anyone can take a side, and the currency buys nothing.
- [Prediki](https://predictionmarkets.tools/tools/prediki.md) — A wiki with a market attached — anyone writes the question, edits it, votes the result.
- [Social Science Prediction Platform](https://predictionmarkets.tools/tools/social-science-prediction-platform.md) — Forecast what a study will find, before it finds it, and be scored against the estimate.
- [Confido](https://predictionmarkets.tools/tools/confido.md) — Open-source forecasting workspace you host yourself, with a Brier score pointing upwards.
- [Fatebook](https://predictionmarkets.tools/tools/fatebook.md) — Write down what you think will happen, in Slack or a browser, and get scored on it.
- [Good Judgment Open](https://predictionmarkets.tools/tools/good-judgment-open.md) — Brier scores against the crowd, and the recruiting ground for Superforecasters.

## Named as a replacement for

- [INFER](https://predictionmarkets.tools/alternatives/infer.md)
- [Kalshi](https://predictionmarkets.tools/alternatives/kalshi-alternatives.md)
- [PredictionBook](https://predictionmarkets.tools/alternatives/predictionbook.md)
- [Trepa](https://predictionmarkets.tools/alternatives/trepa.md)