The short version
- The Nasdaq Composite covers almost all companies listed on the Nasdaq exchange; the Nasdaq-100 tracks about 100 of the largest non-financial ones.
- Both are weighted by market value, so the biggest companies move the index the most.
- You cannot buy an index directly; funds that track it are the usual route, and their concentration is worth understanding.
When a news report says "the Nasdaq index fell today", it is almost always referring to one of two benchmarks run by Nasdaq, the US exchange operator: the Nasdaq Composite or the Nasdaq-100. They overlap heavily but are not the same thing, and the difference matters if you ever buy a fund that tracks one of them. This guide explains what each measures, how the numbers are calculated and how to read them sensibly.
The Nasdaq Composite index
The Nasdaq Composite index includes nearly all common shares listed on the Nasdaq stock market, which amounts to several thousand companies from technology, healthcare, consumer, financial and other sectors, US and foreign. Because it is so broad, it is often used as a gauge of how Nasdaq-listed shares as a whole are doing.
It is weighted by market capitalisation: each company counts in proportion to its total market value. The largest companies therefore have a far bigger influence on the index than the thousands of smaller ones.
The Nasdaq-100 (NDX)
The Nasdaq-100 tracks roughly 100 of the largest non-financial companies listed on Nasdaq; banks and other financial companies are excluded. Its ticker symbol is NDX, and some quote services display it with an exchange prefix, such as INDEXNASDAQ NDX or INDEXNASDAQ: NDX. Membership is reviewed at least once a year, with companies added or removed according to size and eligibility rules.
The Nasdaq-100 uses a modified market-capitalisation weighting: it starts from market value but caps the weight of the very largest members so that no single company, or small group of them, can dominate beyond set limits. Even so, a handful of companies make up a large share of the index, which makes it more concentrated than broader benchmarks such as the S&P 500.
| Nasdaq Composite | Nasdaq-100 | |
|---|---|---|
| Members | Nearly all Nasdaq-listed common shares | About 100 of the largest non-financial Nasdaq companies |
| Financial companies | Included | Excluded |
| Weighting | Market capitalisation | Modified market capitalisation, with caps |
| Symbol often shown | COMP or IXIC, depending on the data provider | NDX |
How weighting moves the number: an illustration
Imagine a tiny index of three companies worth $600 billion, $300 billion and $100 billion: weights of 60%, 30% and 10%. On one day the largest rises 5%, the middle one is flat and the smallest falls 10%. The index changes by (0.6 × 5%) + (0.3 × 0%) + (0.1 × −10%) = 3% − 1% = +2%, even though two of the three companies did not rise. That is exactly how a few very large companies can pull the real Nasdaq indices up or down on days when most members move the other way. The numbers here are purely illustrative.
Reading the Nasdaq index price, live and today
An index is not traded itself; it is a number calculated from its members' prices. The official index level is calculated during regular Nasdaq trading hours, 09:30 to 16:00 New York time, Monday to Friday. Our market hours board shows whether New York is in session now.
- Nasdaq index live: during the session, the level updates continuously as member shares trade. Some free websites show delayed data, so check whether a quote is marked real-time or delayed.
- Nasdaq index today: the daily change is measured against the previous day's official close. A move of 300 points on an index at 20,000 is a 1.5% change; percentages are more meaningful than points when comparing days or indices.
- Nasdaq index price outside hours: before the open or after the close, the numbers you see are usually futures contracts or pre-market indications, not the official index. They hint at sentiment but can change completely once trading begins. See our guide to futures for how these contracts work.
Investing in a Nasdaq index
You cannot buy an index directly. Investors usually gain exposure through index funds or ETFs that hold the member shares in line with the index weights. Before choosing one, compare:
- Which index it tracks: Nasdaq-100 funds are far more concentrated than broad US or global funds.
- The expense ratio and any platform or dealing costs; see trading fees explained.
- Tracking difference: how closely the fund has followed its index after costs.
- Currency: if your home currency is not the dollar, exchange-rate moves add to or subtract from returns.
- Income treatment: whether dividends are paid out or reinvested.
A single concentrated index can fall sharply when its largest members fall together. Many investors therefore treat a Nasdaq-100 fund as one part of a diversified portfolio rather than the whole of it. For the basics of shares and funds, read how the stock market works.
What about the Nasdaq crypto index?
Nasdaq also publishes indices outside the share market. The Nasdaq crypto index, officially the Nasdaq CME Crypto Index (NCI), is designed to measure the performance of a basket of large digital assets. It is entirely separate from the Composite and the Nasdaq-100 and contains no company shares. Crypto-assets are highly volatile; read how crypto works before considering any product linked to them.
The same caution applies to any product that combines the Nasdaq name with crypto or leverage. A familiar brand on an index does not change the risk of what it measures, so always check exactly what an index or fund holds before you rely on its name.
Reader questions
Is the Nasdaq the same as the Nasdaq-100?
No. Nasdaq is the exchange operator. The Nasdaq Composite covers nearly all shares listed on its market, while the Nasdaq-100 tracks about 100 of the largest non-financial companies.
Why does the Nasdaq sometimes rise when most of its stocks fall?
Both main Nasdaq indices are weighted by market value, so strong moves in a few very large companies can outweigh declines in many smaller ones.
Can I trade the Nasdaq index at night?
The index itself is only calculated during regular trading hours. Outside them, futures contracts and some other products based on the index continue to trade.
Sources
- Nasdaq Global Indexes, Nasdaq-100 and Nasdaq Composite methodology overviews
- Nasdaq Global Indexes, Nasdaq CME Crypto Index (NCI) overview