---
title: "Overview"
description: "What Challenge is, which half of the integration you build and which half Challenge runs, the whole loop in two snippets, the vocabulary, and a map of every documentation page."
url: https://www.withchallenge.com/docs/overview
canonical_markdown: https://www.withchallenge.com/docs/overview.md
docs_index: https://www.withchallenge.com/llms.txt
api_version: v1
lastUpdated: 2026-09-22T16:56:18.000Z
---
# Overview
Challenge lets a player pay a fee to attempt a fixed standard in your game, and pays them a fixed prize when they beat it.
Challenge funds the prize, announces it before the player pays, and never pools one player's fee into another player's winnings. There is no opponent, no wager and no pot. There is a bar, a fee to try it, and a prize for clearing it.
You add two script tags and one server handler. Challenge does the rest.
## What you build, what Challenge runs
The integration has two halves and one hard line between them.
| Side | Holds | Does |
|---|---|---|
| Your game, in the browser | The program ID, which is public | Mounts Challenge.js, records ordinary rounds, starts paid rounds |
| Your server | The secret key (`sk_test_`, `sk_live_`) | Receives finished rounds and reports the measurement to `/v1` |
| Challenge | Everything else | Accounts, money, the bar, the verdict, every player-facing screen |
Challenge runs all of the following, and none of it is yours to build:
- Accounts, sign-in and single sign-on across games
- Age and identity verification
- Deposits, balances, withdrawals and the ledger behind them
- Responsible gaming limits and self-exclusion
- The arming flow, the fee confirmation and every result screen a player sees
- Measuring a Challenge's bar from real rounds, then monitoring it for drift
- Publishing the next rung when a player claims one, and pricing it
- Funding and paying the prize
What you build is three calls in the browser and one HTTPS request from a server you control.
## The integration at a glance
The browser half. Two script tags and one call, then one line at the end of every round, then one line to start a paid round.
```html
```
```javascript
Challenge.init({ program: '<>' })
// At the end of every round, paid or free, signed in or not.
Challenge.record('moves', 34)
// When the player has armed a Challenge on the island and a paid round begins.
const attempt = await Challenge.startAttempt()
// { attemptId, feeCharged, prizeOffered, threshold, thresholdDirection }
```
The server half. One request, with your key, once the round is finished.
```javascript
// The key lives on your server. It never reaches the browser.
const settled = await fetch(
`https://api.withchallenge.com/v1/attempts/${attemptId}/outcome`,
{
method: 'POST',
headers: {
'Content-Type': 'application/json',
'X-API-Key': process.env.CHALLENGE_API_KEY,
'Idempotency-Key': attemptId,
},
body: JSON.stringify({ score: 34 }),
}
)
```
Nothing is relayed back to your game. Challenge applies the bar it froze onto the attempt, pays the prize if it was met, and the island renders the result on its own.
Three rules decide where money can be created, and every other part of the API follows from them: scores enter the money system only from an authenticated partner server, fees are charged before scores are heard, and the bar and the prize freeze at the start of the attempt. [The trust model](https://www.withchallenge.com/docs/trust-model.md) states each one and what it forbids.
## Key vocabulary
| Term | Meaning |
|---|---|
| Program | Your game, as Challenge knows it. The program ID is public and goes in the browser. |
| Challenge | The product unit. One standard a player can attempt: a metric, a bar, a fee and a prize. Never called a challenge. |
| Metric | What is measured, in your game's own units: moves, seconds, points. |
| The bar | The threshold a score is judged against, and its direction. Measured from real rounds by Challenge, never chosen by hand, because a bar you picked would set the pass rate, which would set what Challenge expects to pay. |
| The island | The Challenge surface that sits over your game. It shows what is on offer, takes the fee confirmation, and renders the result. It is Challenge's, not yours: you never draw a fee, a balance or a verdict. |
| Attempt | One paid try. Created with the fee charged and the bar frozen, settled by an outcome, expired and refunded if no outcome arrives within an hour. |
| Arm | A player agreeing to a Challenge and its fee, on the island, by their own tap. There is no API to arm for them, because agreeing to a price is the player's act. |
| Outcome | The score your server reports, plus Challenge's determination of whether it met the frozen bar. |
| Award | The prize paid when it did. |
| Calibration | The free period a new Challenge spends collecting rounds before it can charge. |
| Rung | A harder Challenge, worth twice the one below it, unlocked by claiming that one. Spawned and priced by Challenge. |
| Integrity tier | The prize ceiling and verification level for your program. It does not decide who reports a score. |
| Program key | `sk_test_` for sandbox, `sk_live_` for production. Server side only, always. |
| player_ref | Your own identifier for a player, used when your server creates attempts through `/v1`. |
## The documentation set
Start with the [Quickstart](https://www.withchallenge.com/docs/quickstart.md) if you want a settled attempt in front of you within the hour. Read [How a round works](https://www.withchallenge.com/docs/how-a-round-works.md) first if you want to understand the loop before you write any of it.
### Get started
| Page | What it answers |
|---|---|
| [Overview](https://www.withchallenge.com/docs/overview.md) | What Challenge is, what you build versus what Challenge runs, where everything else is |
| [Quickstart](https://www.withchallenge.com/docs/quickstart.md) | The shortest path from an unmodified game to a settled attempt in sandbox |
| [How a round works](https://www.withchallenge.com/docs/how-a-round-works.md) | The full lifecycle of one paid round, as a sequence, actor by actor |
| [The trust model](https://www.withchallenge.com/docs/trust-model.md) | The three rules, what each forbids, and what each means for your code |
### Concepts
| Page | What it answers |
|---|---|
| [Programs and keys](https://www.withchallenge.com/docs/programs-and-keys.md) | Program ID versus `sk_test_` and `sk_live_`, which surface each may touch, approval and rotation |
| [Challenges](https://www.withchallenge.com/docs/challenges.md) | Metric, threshold, direction, fee, prize, and the status machine behind them |
| [Calibration](https://www.withchallenge.com/docs/calibration.md) | How a bar is measured, the three paths to one, the provisional cap and the prize ramp |
| [The Challenge ladder](https://www.withchallenge.com/docs/challenge-ladder.md) | Rungs, claim to unlock, prize doubling, and where locked rungs are listed |
| [Tournaments](https://www.withchallenge.com/docs/tournaments.md) | House-funded fixed purses, rounds, entry rules, minimum fill and rank settlement |
### Build
These pages are being written. Until they land, the [Quickstart](https://www.withchallenge.com/docs/quickstart.md) and the [Challenge.js reference](https://www.withchallenge.com/docs/challenge-js.md) carry the browser half and the `/v1` [API reference](https://www.withchallenge.com/docs/api.md) carries the server half.
| Page | What it will answer |
|---|---|
| Install Challenge.js | The two scripts, `init({ program })`, anchors, theme, SPA mount and `destroy()` |
| Record rounds | `Challenge.record(metric, score)`, why it ships before anything chargeable, limits, metric naming |
| Start a paid attempt | Arming, `startAttempt()`, the frozen fields it returns, branching on `.code` |
| Report the score from your server | `POST /v1/attempts/{id}/outcome`, both server templates in full |
| Server-created attempts | `POST /v1/players` and `POST /v1/attempts`, only for games with no browser client |
| Webhooks | Handler, registration, signature verification, retries, debugging |
| Real-time settlement | What Challenge.js already does, and when you need none of it |
### Test and go live
| Page | What it answers |
|---|---|
| [Sandbox](https://www.withchallenge.com/docs/sandbox.md) | Test keys, the money-free loop a calibrating Challenge gives you, sandbox versus production |
| Simulate a Challenge's life | The portal batch simulator, its controls, and a worked drift suspension |
| Go-live checklist | Approval, key swap, ceilings, ramp, webhook verification, error branching |
### Reference
| Page | What it answers |
|---|---|
| [Challenge.js](https://www.withchallenge.com/docs/challenge-js.md) | Every option, method, error code and catalog element in the browser half |
| [API](https://www.withchallenge.com/docs/api.md) | All of `/v1`: authentication, decimal-string money, idempotency, the error contract |
| Webhook events | Every event with its payload, trigger condition and delivery semantics |
| Errors | The full catalog, grouped by surface, with cause and fix for each code |
### For AI coding agents
An agent integrating Challenge in one pass should fetch `/integrate.md`, which is self-contained and executable with no further fetches, and `/llms.txt` for the index and the standing instructions. Both are generated from these pages, so neither can drift from them.
---
Source: https://www.withchallenge.com/docs/overview.md
Docs index for AI agents: https://www.withchallenge.com/llms.txt