Market data glossary

Quotes and prices

The basic units of a price stream and the words used to describe how fresh they are.

• Tick - a single price update for one instrument, with a timestamp. A feed is a stream of ticks.
• Quote - the current price of an instrument as offered by the market. On a two-sided market a quote has a bid and an ask; elsewhere it is a single price.
• Bid - the best price at which someone is ready to buy right now. If you sell immediately, you get the bid.
• Ask - the best price at which someone is ready to sell right now, also called the offer. If you buy immediately, you pay the ask.
• Spread - the difference between ask and bid. It is the cost of an immediate round trip. See bid, ask and spread for brokers.
• Mid price - the midpoint between bid and ask, (bid + ask) / 2. Nobody trades at it, but it is a fair single number for the market level.
• Last price - the price of the most recent trade or the published reference price. In FinaQuotes, crypto, indices, commodities and bonds carry the last price, and bid = ask = last in the tick.
• Trade - a completed transaction at a price and size. A trade tells you where the market dealt, not where you can deal now.
• Snapshot - the latest known state of an instrument at one moment, usually requested once to fill a screen before live updates start.
• Real-time data - prices delivered as soon as the provider receives them. In the FinaQuotes feed a tick is delivered sub-second after receipt.
• Delayed data - the same prices released after a deliberate, fixed lag. The data is accurate for its time but not current.
• 15-minute delay - the most common delay for exchange data shown on public pages. FinaQuotes free widgets show stocks, indices, commodities and bonds with this delay. See real-time vs delayed market data.

Candles and time

How a stream of ticks becomes a chart, and why time zones matter.

• OHLC - open, high, low and close: the first, highest, lowest and last price within a period.
• Candle - one OHLC bar for one period, drawn as a body and wicks. Also called a bar or a candlestick. See how candles are built from ticks.
• Timeframe - the length of the period one candle covers. FinaQuotes delivers 1m, 5m, 15m, 30m, 1H, 4H, 1D, 1W and 1MN.
• Aggregation - building longer candles from shorter ones. Higher timeframes are aggregated from a 1-minute base, so all timeframes agree with each other.
• Session - the hours during which a market trades, also called trading hours. Stock candles exist only within the session of the exchange where the stock is listed.
• DST - daylight saving time. Exchange hours move against UTC when local clocks change, so session-aware candles must follow the local calendar.
• UTC timestamp - a time stated in Coordinated Universal Time, without a local offset. All FinaQuotes timestamps and candles are in UTC.
• Backfill - loading missing history to close a gap, for example after a reconnect or when a chart opens. Candle history is loaded over REST; see historical data.

Delivery and protocols

How prices travel from the provider to your system.

• Market data feed - a continuous stream of prices pushed to your system as they change. See what is a market data feed.
• Market data API - an interface you call to request data, such as history or an instrument list. A feed pushes, an API answers.
• WebSocket - a protocol that keeps one connection open in both directions, so the server can push each tick as it happens. It is the usual transport for live prices.
• REST - request-response access over HTTP. It suits history, catalogues and occasional lookups. See WebSocket vs REST for market data.
• Subscription - a request on a stream connection to receive updates for chosen instruments. You subscribe to what you show and unsubscribe from the rest.
• Heartbeat - a small periodic message that confirms a connection is alive when no prices are moving.
• Reconnect - opening a new connection after the previous one dropped, then restoring subscriptions and backfilling any gap.
• API key - the credential that identifies your account. Keep it on the server and never put it in browser code.
• HMAC - a way to sign a request with a secret key, so the server can verify it without the secret being sent. The FinaQuotes WebSocket uses HMAC authentication.
• Rate limit - the maximum number of requests allowed in a period. FinaQuotes REST allows 120 requests per minute per IP by default; the stream has no per-message billing.
• 429 - the HTTP status Too Many Requests, returned when a rate limit is exceeded. Wait and retry with a growing pause rather than in a tight loop.

Field formats and endpoints are in the documentation.

Reliability

Terms you meet in the reliability section of any provider evaluation.

• Redundancy - having more than one independent source or component for the same job, so one failure does not stop the service.
• Failover - the automatic switch to a backup source when the primary one fails or goes silent. FinaQuotes uses several independent sources per asset class with automatic fallback.
• Uptime - the share of time a service is available. FinaQuotes targets 99.9% uptime; see reliability.
• SLA - service level agreement: the written commitments on availability and response times, and what happens if they are missed.

Widgets and embedding

Words used when quotes are shown on a website.

• Widget - a ready interface block, such as a ticker tape or a quote table, that shows live prices on a page. See ticker tape vs quote table vs chart.
• Embed, iframe - an embed is code you paste into a page to show content served from elsewhere; an iframe is a frame that holds that content in isolation from your page. Free FinaQuotes widgets are embedded as an iframe.
• Attribution - a visible credit to the data or widget provider. Free widgets carry a small by FinaQuotes line.
• White-label - a product delivered under your brand, without the provider name. See Widgets Pro and white-label market data.

Markets and instruments

How instruments are named, grouped and described.

• Symbol - the short code that identifies an instrument, such as EURUSD or AAPL.
• Instrument - anything with a price in the feed: a currency pair, a stock, a cryptocurrency, an index, a commodity or a bond.
• Asset class - a group of instruments of the same kind. FinaQuotes covers seven: stocks, crypto, forex, metals, commodities, indices and bonds. See coverage.
• Catalogue - the list of available instruments with their symbols, names, asset classes and precision. See the instrument catalogue.
• Normalization - bringing data from different sources into one format: the same symbols, fields, timestamps and precision. FinaQuotes data is aggregated from multiple institutional and exchange data sources and normalized by FinaQuotes.
• Liquidity - how easily an instrument can be bought or sold without moving its price. FinaQuotes is not a liquidity provider: it supplies prices, not trade execution.
• Spot - a price for immediate delivery, as opposed to a future date. Spot metals and spot forex are quoted this way; see metals and forex.
• Futures-based commodity - a commodity whose reference price comes from futures contracts rather than spot trades, which is common for energy and agricultural markets. See commodities.
• Index value - the calculated level of an index, such as a stock index. It is computed from its constituents and is not traded directly. See indices.
• Benchmark - a reference price or index that other prices and performance are measured against.
• Tracker, ETF - a fund, often exchange-traded (ETF), that follows an index or a commodity. Its price is close to the underlying level but not the same, so do not mix the two on one chart.

This glossary explains terms; it is not investment advice.

Frequently asked questions