Heatmap Chart

Free Online Heatmap Chart Maker

What is a Heatmap Chart?

A heatmap chart uses a color-coded matrix to display values across two dimensions — rows and columns — so patterns, hotspots, and outliers surface immediately without reading individual numbers. Each cell's color intensity maps directly to its value, letting you compare dozens of data points at once. Use a heatmap when you need to reveal correlations, seasonal trends, or performance gaps across categories that would be invisible in a bar or line chart.

Key Features

9 Built-in Color Schemes

Choose from Viridis, Plasma, Turbo, Reds, Blues, and more — or set your own custom min and max colors to match your brand or highlight specific value ranges.

Row and Column Labels

Label both axes clearly so every cell is uniquely identifiable. Toggle row labels, column labels, or both depending on your layout.

Cell Value Display

Optionally show numeric values inside each cell for precise reading alongside the color encoding, with adjustable font sizes.

Interactive Tooltips

Hover over any cell to see its exact value without adding clutter to the visual — ideal for dense matrices with many data points.

Adjustable Cell Layout

Control cell size, gap, border width, border radius, and border color to fit any data density and presentation context.

Color Legend

A built-in legend maps color to value ranges so readers can decode the scale independently. Position it at the top, bottom, left, or right.

Best For

Sales performance across products and time periods

Website engagement by page section and day of week

Student grade distributions across subjects and cohorts

Temperature or sensor readings over time and location

Feature usage rates across user segments and product areas

Correlation matrices in data analysis and research

When to Use

Your data is organized by two categorical dimensions (rows × columns)
You want to reveal patterns visually rather than through a table of numbers
You have too many values to compare individually with bar or line charts
You need to highlight hotspots, gaps, or outliers across a matrix
Readers need to spot trends across both dimensions simultaneously
Color encoding communicates the story faster than exact numbers

Common Mistakes

Using too many rows or columns, making cells too small to read or interact with
Choosing a color scheme with poor contrast that doesn't work for colorblind readers
Omitting the color legend, leaving readers unable to decode what the colors mean
Placing categories with no natural ordering on the axes, which hides meaningful patterns
Comparing groups of very different sizes without normalizing the values first
Showing raw counts when percentages would make cross-row comparisons fair

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Templates

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