What Level 1 includes
Level 1 provides the essential elements of a market: the best bid, the best ask, and the most recent trade, usually with their sizes. This is enough to show the current prices at which the asset can be bought or sold and where the last transaction occurred. It combines the quote and the last price, which is sufficient for most displays.
Level 1 versus Level 2
The difference is depth. Level 1 stops at the best bid and ask, the top of the book, while Level 2 shows multiple price levels of resting orders on each side. Level 1 can be regarded as the summary and Level 2 as the detail beneath it. Most applications use Level 1, as the additional depth is relevant only to certain tasks.
Which applications Level 1 serves
For charting, watchlists, price alerts, portfolio valuation, and most general trading, Level 1 is sufficient. It provides the current price, the spread, and the most recent trade, and supports the construction of OHLCV bars and most derived metrics. Unless resting orders behind the best prices must be observed, Level 1 covers the majority of cases efficiently.
What Level 1 omits
Because it shows only the top of the book, Level 1 does not indicate how much size rests behind the best bid and ask or how the book is distributed on each side. That deeper view, used to assess liquidity and how a larger order might affect the price, is provided by Level 2. Level 1 is a concise summary rather than the full order book.
Top-of-book data on SiftingIO
SiftingIO focuses on clean top-of-book pricing and an aggregated fair price across stocks, forex, crypto, and commodities, delivered under one schema over REST and WebSocket. This provides the best prices and the most recent trade required for charts, tickers, and valuation, reconciled across multiple venues rather than tied to a single one.