SectorsUpdated daily after close · as of 2026-10-19
Market Heatmap: Top 100 US Stocks & Thematic Sector Treemaps
Box size encodes market cap (shares × latest close, recomputed daily); color encodes return over the selected window, clamped at ±5%. Switch to the sector view for curated thematic maps — AI, cloud, cybersecurity, defense, EVs, quantum, and more.
Today's reading
As of market close on October 19, 2026, 41 of the top 100 US stocks by market cap closed higher (41% green), with 7 of the 10 largest names up. Best performer: SNDK +5.53%; worst: SCHW -2.59%. Box sizes reflect live market caps (shares × latest close); the largest is NVDA.
Sources, methodology & freshnessDaily closes for ~5,500 stored symbols + Polygon shares-outstanding reference · Daily after market close (~1:30 PM PT)Data as of 2026-10-19 · Open ↓Close ↑
Source
Daily closes for ~5,500 stored symbols + Polygon shares-outstanding reference
Methodology
Treemap: area = shares × latest close; color = 1d/7d/30d return, clamped ±5%
Updates
Daily after market close (~1:30 PM PT)Data as of 2026-10-19
Maintained & reviewed by Yuriy Matso — methodology shown on the page.
The answer · daily2026-10-19market close
41%green
41 of 100 top stocks gained; the median return was -0.28%.
Mixed tape · 7/10 largest names higher
Equal-count breadth among the top 100; the treemap itself remains market-cap weighted. Returns are close to close.
-5%
+5%
The answer · daily2026-10-19market close
41%green
41 of 100 top stocks gained; the median return was -0.28%.
Mixed tape · 7/10 largest names higher
Equal-count breadth among the top 100; the treemap itself remains market-cap weighted. Returns are close to close.
01
About this map
How Market Heatmap Works
- 1Size every box by live market capMarket cap is recomputed daily as shares outstanding × the latest close from our own price database, so box sizes track the actual market rather than a stale snapshot. The Top 100 view ranks the entire cap universe each evening.
- 2Color every box by returnCell color encodes the selected return window — daily, weekly (7 calendar days), or monthly (30 calendar days) — on a red-to-green scale clamped at ±5%. Deep green/red means a move of 5% or more.
- 3Slice by theme as well as sizeThe By Sector view renders a separate treemap per curated theme — AI & Machine Learning, Cloud & SaaS, Cybersecurity, Defense, EVs, Energy Storage, Fintech, Quantum Computing, Clean Energy, and Semiconductors — so you can see rotation within the themes that actually drive flows.
Who Uses Market Heatmap
Morning Scanners
One glance answers "what kind of day was it?" — broad green, broad red, or a split tape where mega-caps masked weakness underneath.
Theme Traders
The sector maps show rotation between themes: quantum red while defense is green is a real risk-appetite signal you can't see in index charts.
Swing Traders
Switch to the weekly/monthly windows to spot leaders holding gains while the index chops — relative strength at a glance.
Pro Tips
01
Compare the daily and monthly views back-to-back
A stock red today but deep green on the month is a pullback in an uptrend; green today but red on the month is a bounce in a downtrend. The pair of views separates noise from trend in two clicks.
02
Watch the biggest boxes for index direction
The top ~10 boxes are most of the S&P 500's weight. When they disagree with the rest of the map, the cap-weighted index is hiding the real breadth — cross-check the A-D line.
03
Use sector maps for pair ideas
Within a theme, the outlier (one red box in a green sector) is either tomorrow's laggard catch-up trade or the name with a real problem — worth the 30 seconds to find out which.
Common Issues & Solutions
A stock I expected is missing from Top 100▾
The universe is built from our cap database (Polygon shares-outstanding snapshot × live prices). Recent IPOs or symbols missing from that snapshot won't rank until the next shares refresh. GOOGL is deliberately excluded as a duplicate of GOOG.
Sector boxes look too similar in size▾
A few thematic names lack shares-outstanding data; they're sized with a price-based placeholder so they stay visible. Treat sizes in sector view as approximate for the smallest names.
Returns look small on a big news day▾
Data is end-of-day. Intraday moves show up after the next close. This is a daily-close instrument and does not track the live tape.
Frequently Asked Questions
What is a market heatmap?▾
A treemap visualization of the stock market: each rectangle is one stock, its area proportional to market capitalization and its color encoding return over a chosen window. It compresses hundreds of price moves into one picture — the fastest way to see whether a move was broad or narrow, and which themes led.
How are the boxes sized?▾
By market capitalization, recomputed daily as shares outstanding × the latest closing price from our ~5,500-symbol database. Shares-outstanding data comes from a Polygon reference snapshot; prices update every close.
What do the colors mean?▾
Return over the selected window — daily, weekly (7 calendar days), or monthly (30 calendar days) — on a red-to-green gradient clamped at ±5%. Gray cells lack return data for that window.
What are the sector maps?▾
Curated thematic groups (AI & Machine Learning, Cloud & SaaS, Cybersecurity, Defense, EVs & EV Infrastructure, Energy Storage, Fintech, Quantum Computing, Clean Energy, Semiconductors) rather than formal GICS sectors. Themes are where rotation actually happens; the GICS view lives on our Sector Health dashboard.
How often does it update?▾
After every market close, alongside the rest of the daily pipeline. The timestamp under the title shows the data's as-of close.