Build an odds comparison site

What a valid comparison needs

The biggest price is not always the best price.

An odds comparison API is useful only when the event, period, market, selection, line and settlement contract match. Miss one field and a clean-looking table can recommend a different bet.

Prove equivalence first. Then rank the prices.

What the contract gives you

The false-comparison test

These illustrative prices show why the line matters.

Build the comparison key first

Do not group by team name and market label. Match the fields that define the bet.

Build it in six steps

Start with one event and a small bookmaker set.

1. Choose one event

   Find a covered event and keep its canonical event_id.

2. Request a complete snapshot

   Request the bookmakers and markets you need, then follow next_cursor until complete is true.

3. Build an exact comparison key

   Match the event, market group, selection, period, metric, line, side and settlement contract.

4. Reject unusable prices

   Remove unavailable prices, incomplete market groups and rows outside your freshness policy.

5. Render the best valid price

   Rank prices only inside an exact comparison group and preserve ties.

6. Keep the board current

   Start from the snapshot resume token, apply stream deltas and reload after resync.

Request a complete snapshot

curl --request GET \
  --header "X-API-Key: $ODDS_API_KEY" \
  "https://api.odds-api.net/v1/events/{event_id}/odds/snapshot?bookmakers=pinnacle,draftkings,fanduel&market_keys=moneyline,handicap,total&periods=full%20time&include_unavailable=true&limit=2000"

function stable(value) {
  if (Array.isArray(value)) return `[${value.map(stable).join(",")}]`;
  if (value && typeof value === "object") {
    const pairs = Object.keys(value).sort()
      .map(key => `${JSON.stringify(key)}:${stable(value[key])}`);
    return `{${pairs.join(",")}}`;
  }
  return JSON.stringify(value ?? null);
}

function comparisonKey(eventId, row) {
  return [
    eventId,
    row.market_group_id,
    row.selection_key,
    row.period_str ?? row.period,
    row.bet_type,
    row.metric,
    row.line ?? "",
    row.side ?? "",
    row.player_name ?? "",
    stable(row.market_contract),
    stable(row.selection_parameters),
  ].join("|");
}

function bestValidPrices(snapshot) {
  const groups = new Map();

  for (const row of snapshot.items) {
    if (!row.is_available || typeof row.odds !== "number") continue;
    const key = comparisonKey(snapshot.event_id, row);
    const current = groups.get(key) ?? [];
    if (!current.length || row.odds > current[0].odds) groups.set(key, [row]);
    else if (row.odds === current[0].odds) current.push(row);
  }

  return [...groups.entries()].map(([key, books]) => ({
    key,
    best_odds: books[0].odds,
    books,
  }));
}

Show freshness per bookmaker

Use bookmaker_as_of_ts_ms for each book. Compare it with the current time and target_refresh_interval_seconds.

Snapshot first. Stream when it matters.

A stream is not a complete board. Load the REST snapshot, save resume, then apply deltas.

Use SSE for one-way updates or WebSockets where they fit your stack. Both use the same update contract.

Read the REST, SSE and WebSocket guide.

Lay out the comparison screen

Show the bet, the best valid price and its age without a tooltip.

Use the API commercially

Paid plans support customer-facing comparison products. Pre-match odds only. Your product owns the interface and customer experience.

Raw-feed resale, bulk redistribution and API-key sharing are not included. Read the API Terms and Data License before launch, then use the current pricing limits to model requests and stream hours.

Odds comparison API questions