How to verify live market data

Five questions to ask about any quoted price

1. Which venue or benchmark is it from? “The gold price” could be an LBMA auction price, a futures settlement, a dealer's retail quote, or a crypto token. These are different numbers.
2. What is the timestamp? Not “updated 2 minutes ago” for the page — when was the underlying value observed? Pages often refresh a cached value.
3. Is it a mid, a bid or an ask? You can never transact at the mid. For anything you intend to buy or sell, the spread is part of the price.
4. Is it aggregated? Crypto prices are usually volume-weighted across many exchanges, so no single venue will match exactly.
5. What happens when the source fails? Good pages say “stale” or “unavailable”. Bad ones silently show yesterday's number as though it were live.

How FinSage's own data works — and what is wrong with it

Auditing this site is a concrete example. The chain is short and fully documented:

• Crypto and gold: a serverless function on this site calls the CoinGecko public API for a fixed list of assets, and the response is cached for 90 seconds at the CDN and again in your browser's local storage. Your browser never contacts CoinGecko directly.
• Exchange rates: the same pattern against open.er-api.com, cached for 6 hours, because that provider itself refreshes only about once a day.
• Failure behaviour: if a fetch fails, the page falls back to the last cached values and labels them, or shows an explicit “temporarily unavailable” message. It does not invent numbers.

Two further honest caveats: the exchange rates are up to a day old by design, which is fine for understanding a bank's markup and not fine for timing a large transfer; and free public APIs have outages, so “temporarily unavailable” is a normal state, not a bug.

How to cross-check in practice

1. Compare two independent sources. Not two sites that both resell the same aggregator — check what each says its source is.
2. Go upstream. Most public APIs can be opened directly in a browser; the raw response usually carries its own timestamp.
3. Use the official benchmark where one exists: LBMA for gold, central banks for FX reference rates, the index provider for an index level.
4. Check the spread for anything transactable — a mid price is not a dealable price.
5. Watch for stale caching. Reload and see whether the timestamp actually moves.

Red flags on a data page

• No timestamp, or only a relative one (“just now”) with no absolute time.
• No named source, or a vague “market data providers”.
• A price that never changes across reloads on a market that is open.
• Precision that exceeds plausibility — six decimal places on an illiquid asset.
• Prices presented alongside “signals”, “predictions” or affiliate trading links. The data is there to sell you something.
• Aggregated crypto prices presented as though they were a single exchange's, or futures presented as spot.

Matching data quality to the decision

Not every use needs the same rigour:

• Curiosity or education — a cached, aggregated number is perfectly adequate. That is what this site provides.
• Budgeting a trip or estimating a transfer — a daily rate is fine, but assume you will receive 1–3% less than mid-market. See how conversion fees work.
• Actually transacting — use the venue or provider you are transacting through, at the moment you transact, and look at the executable price rather than a reference one.

The rule that follows: never place a trade or transfer on the strength of a number you read on a content site, including this one. Use content sites to understand; use the venue to act.