A heatmap is a grid of colored cells where each color shows the size of a number. Warmer or darker colors usually mean bigger values and cooler or lighter colors mean smaller values, so you can spot patterns across a lot of data at a glance.

Paste your numbers separated by commas, choose how many columns you want, and the tool arranges the values into a grid and colors each cell by size. You can then edit the palette, labels, and size, and download the image.

Yes. It is completely free, runs entirely in your browser, needs no sign-up, and never sends your data to a server.

Yes. Open the Upload CSV tab, pick your file, and choose the column you want to map. The tool reads the file locally and lets you select which column becomes the heatmap.

It depends on your data. For weekly patterns use 7 columns, for months use 12, and for a general grid pick a number that makes the grid close to square. You can change the column count any time.

Viridis and Magma are good defaults because they read well and are friendly to colorblind viewers. Use a diverging palette like Cool-Warm when your data has a meaningful midpoint, such as positive versus negative values.

The color legend, or colorbar, links each color to a value. The bottom of the bar is your minimum and the top is your maximum, so you can read any cell's rough value from its color.

Yes. Turn on Show value in each cell. You can also set the number of decimal places and let the tool pick light or dark text automatically for readability.

One very large value can flatten the rest of the colors. Set a manual color scale max just below the outlier so the smaller values keep their detail, and mention the capped scale in your caption.

Yes. Set the export width and height, then click Download PNG, JPEG, or WebP. Larger export sizes give sharper images for print and journals.

Not exactly. A correlation matrix is one common use of a heatmap, where each cell is a correlation value. A heatmap is the general picture; a correlation matrix is one thing you can put in it.

A heatmap colors a grid of cells, while a choropleth colors regions on a geographic map. Both use color for value, but a heatmap is for tables and grids, not maps.

Yes. Values fill the grid left to right, then top to bottom. If your rows or columns have a specific meaning, paste the numbers in that exact order so the layout is correct.

Yes, and it works well for calendar-style views, like days as columns and weeks as rows. For a single trend over time, though, a line chart is usually clearer.

Use Viridis or Magma, which keep their order for most color-vision types, keep cell labels on, and avoid red-green diverging scales when you can.

It reports the count, minimum, maximum, range, mean, median, and standard deviation of your values, so you can describe the data alongside the picture.

The tool already rescales values to a 0 to 1 position for coloring using min-max normalization, so cells are colored fairly across the full range without you doing anything.

No. Everything runs in your browser. Your numbers never leave your device, which makes the tool safe for sensitive data.

Yes. Export a high-resolution image, keep the caption clear, state your color scale range, and the figure is ready for a manuscript or thesis.

If your value count does not divide evenly by the number of columns, the last row is partly filled. That is normal; the tool leaves the extra cells blank rather than inventing data.