Heatmap Chart
Show intensity patterns across rows and columns using a color gradient.
About Heatmap Chart
Visualize data density across two dimensions using a color-coding system. Ideal for activity patterns, performance matrices, and correlation tables. All processing is 100% client-side.
How to Use
- Paste your matrix — copy a table from Excel. Ensure the top-left cell is your row category title.
- Toggle Transpose — use 'Swap X-Y' if you need to flip your data orientation for better readability.
- Set the intensity — the tool auto-detects min/max values to calibrate the color intensity scale.
- Adjust colors — choose a brand anchor color to generate a smooth, professional gradient ramp.
- Configure labels — rotate axis labels or toggle numeric heartbeats within individual matrix cells.
- Export — download as a high-resolution PNG for reports or an exact-match interactive PPTX.
Common Use Cases
- Website Activity Mapping — plot traffic volume by Hour of Day and Day of Week.
- Risk Assessment Matrix — visualize project Risk Impact vs Likelihood across departments.
- Shift Coverage Analysis — identify staffing gaps by plotting counts across time slots and zones.
- Correlation Analysis — visualize the relationship between variables in a compact, color-coded grid.
- Private Business Intelligence — analyze performance heatmaps locally with zero cloud exposure.
Technical Details
Powered by Apache ECharts. Features a dynamic visualMap component that maps values to a continuous color ramp.
Frequently Asked Questions
- How large can my matrix be?
- The tool is optimized for matrices up to 100x100 cells. Larger datasets will automatically hide labels for performance.
- Can I swap the axes?
- Yes, the 'Swap X-Y' button instantly pivots your matrix between horizontal and vertical orientations.
- What data is a heatmap best suited for?
- Heatmaps work well for any dataset organized as a grid of values across two categorical dimensions — such as website engagement by day-of-week and hour-of-day, customer satisfaction scores by product and region, or correlation matrices between multiple variables.
- How do I export my heatmap to PowerPoint?
- Click 'Download PPTX'. The heatmap is exported as a high-resolution image embedded in a PowerPoint slide. The color scale and cell labels are captured exactly as shown, making it ready to drop into a report or board deck without further formatting.
- How should I structure my data for a heatmap?
- Arrange your data in a matrix format: the first column contains row category labels (e.g., days of the week), the first row contains column category headers (e.g., hours), and the remaining cells contain numeric values. You can also paste a flat three-column table (Row, Column, Value) and let the tool pivot it automatically.
- Can I customize the color scale and palette of my heatmap?
- Yes. The heatmap chart lets you choose from several built-in color palettes including sequential scales (e.g. white-to-blue for positive-only data), diverging scales (e.g. blue-white-red for data with a meaningful midpoint such as zero or average), and custom ranges. You can also set min and max bounds for the color scale so that outliers do not wash out the color variation across the rest of the data. All options are previewed live. Charts export as PNG, SVG, or PowerPoint.
Chart Data in PNG — Resume Editing
What is embedded chart data?
PNG exports and shared links may include your original chart data and settings. Anyone with the file or complete link may recover them.
How to use it
- Export your chart to PNG
- Keep the PNG file
- Drop or paste it into the "Resume Chart from PNG" tool any time you need to edit it again
- Your chart restores exactly as you left it — make changes and export again
Why this is better than static images
Other chart tools export PNG images that are final — once exported, you cannot edit them without redoing the work from scratch.
- No need to save the source spreadsheet separately — the PNG IS your backup
- Share a PNG with a colleague and they can restore and edit it without the original data
- Years later, if you need to update a chart, open the PNG and resume — no searching for old files
- For archival: keep PNGs alongside your reports and presentations; they are fully self-contained
Is it secure?
PNG exports and shared links may include your original chart data and settings. Anyone with the file or complete link may recover them.
Embed URL — Interactive Chart for Presentations
What is the Embed URL?
The Embed URL opens a clean, interactive version of your chart in a browser — showing only the chart with no tool interface, no settings panel, and no export buttons. Tooltips and hover interactions work fully. The chart data is encrypted in the URL, just like the Recovery Link.
Where to find it
- Click the "🔗 Embed URL" button on the chart tool page — it copies the URL to your clipboard instantly
- The embed URL is also saved below the slide boundary in your exported PPTX file, labeled "Embed URL — interactive view"
Using the Embed URL in Other Tools
The Embed URL works anywhere that supports iframes or URL embeds:
- Notion — paste the URL as an embed block (type /embed in Notion)
- Confluence — use the HTML macro or iframe macro with the embed URL
- SharePoint — embed via the Embed web part
Any website or intranet page — use a standard HTML iframe:
<iframe
src="YOUR_EMBED_URL"
width="800"
height="500"
frameborder="0"
allowfullscreen>
</iframe>Note on self-hosted deployments: If your organisation uses the self-hosted version of Lokaltools on your intranet, embed URLs point to your internal domain. These will only work for viewers on your company network or VPN — which may be exactly what your IT security team requires.
Chart Colors — Brand-Consistent Palettes in Seconds
Most charting tools give you a fixed color palette you cannot change, or require you to manually pick every color one by one. Lokaltools uses a three-step color system that starts from your company's brand color and builds a complete, harmonious palette automatically.
Step 1 — Brand Anchor
Enter your company's primary brand color as a hex code (e.g. #0066CC) in the Brand Anchor field. This is typically your main logo color, primary button color, or the dominant color from your brand guidelines. The brand anchor color is used as the starting point for all palette generation. Every color in your chart traces back to this single input — so your chart always feels on-brand without manual color selection.
Step 2 — Harmony
The Harmony dropdown selects the color theory rule used to generate the remaining chart colors from your brand anchor. Each harmony produces a different relationship between colors.
| Harmony | What it produces | Best for |
|---|---|---|
| Analogous | Colors adjacent on the color wheel — subtle, cohesive | Single-theme data, when colors should feel similar |
| Complementary | Two colors directly opposite — high contrast | Two-series comparisons, positive vs negative |
| Triadic (Balanced) | Three evenly spaced colors — vivid but balanced | Most business charts, 3-6 data series |
| Split Complementary | One anchor + two colors flanking its complement | Good contrast without full complementary tension |
| Tetradic | Four colors forming a rectangle on the wheel — rich | Charts with 4+ series needing maximum distinction |
Triadic (Balanced) is the default and works well for most business presentations. Switch to Analogous for a more subtle, conservative look, or Complementary when you want two data series to visually contrast strongly (e.g. budget vs actual).
Step 3 — Generated Swatches (Manual Override)
Below the harmony selector, the tool displays 5–6 generated color swatches — these are the actual colors that will appear on your chart. If any individual color does not work, click that swatch to open a color picker and replace it with any color you choose. Manual overrides are preserved in the recovery link.
Background mode (Light / Dark toggle): switches the palette lightness to suit your slide background. This adjusts the generated colors automatically so they remain readable.
Tips for Brand Color Usage
- Finding your exact brand hex code: Check your company's brand guidelines PDF, or right-click your company logo on the website → Inspect → find the CSS color value.
- When to use Analogous vs Triadic: Use Analogous when your chart has one dominant message and you want colors to feel unified. Use Triadic when each series represents a genuinely different thing (e.g. Revenue, Cost, Profit).
- Matching exported chart colors to your PowerPoint template: The PPTX Exact export preserves colors pixel-perfectly — what you see in the browser is exactly what appears in your PowerPoint slide.
Frequently Asked Questions
- Does this tool work offline?
- Yes — once the page has loaded, the tool works fully without an internet connection. The only exception is the Embed URL interactive view, which requires the chart tool page to be reachable when the embed is displayed.
- Can I use this for confidential or sensitive data?
- Yes. Your data is processed entirely in your browser using WebAssembly. It is never sent to Lokaltools servers or any third party. This makes the tool suitable for financial data, patient data, legal documents, and any other sensitive information.
- What data formats can I paste?
- Copy cells directly from Excel, Google Sheets, or Apple Numbers and paste — the tool auto-detects the format. CSV file upload is also supported. Data copied from web pages or PDFs may not paste correctly — clean it in Excel first.
- How do I find my company's brand hex color?
- Check your company's brand guidelines document or open your company website, right-click the logo or a branded button, select "Inspect", and look for a CSS color value starting with #.
- Can I save my brand color so I don't have to re-enter it every time?
- The brand anchor color is saved in the Recovery Link along with all other chart settings. Export your chart, then use the Recovery Link next time to restore your brand color automatically.
- Is the embedded chart data permanent?
- Yes. The embedded data is stored in the PNG file itself — not on any server — so there is no expiry. As long as you have the PNG file, you can restore and edit your chart.
- Can I share the PNG with a colleague?
- Yes — anyone with the PNG file can restore and edit the chart using the "Resume Chart from PNG" tool. Treat the PNG like a shared document: share only with people who should have access to the underlying data.
- What is the difference between embedded PNG data and Embed URL?
- Embedded PNG data contains your full chart state encrypted in the PNG file — you can drop it into the "Resume Chart from PNG" tool to edit and re-export. The Embed URL opens a view-only interactive chart with no editing capability.
Privacy & Security
This tool runs entirely in your browser. Your data follows this path: Your spreadsheet → Your browser → Your exported file. Nothing else. No upload step. No server processing. No analytics on your data content.
Chart PNG exports may contain the original chart data and settings as recoverable metadata. Recovery and embed links contain data and the key needed to open it in the URL fragment. Anyone with the file or complete link may recover that data. Share only with intended recipients. A fragment is normally omitted from HTTP requests, but JavaScript and services you share a link with can read it.
For organisations requiring formal confirmation: Lokaltools cannot read your data, does not store your data, and has no technical mechanism to access your data even if legally compelled to do so. This is not a policy — it is an architectural fact.
Technical Details
Powered by Apache ECharts for high-performance canvas rendering, PapaParse for intelligent CSV and tab-separated data parsing, and PptxGenJS for native OOXML chart objects. Magic link encryption uses the browser's built-in Web Crypto API (AES-256-GCM) with pako compression — no external encryption library required. All processing is 100% client-side. No data is transmitted at any point.
Local processing
Our local file, text and chart tools process content on your device using JavaScript, browser APIs and, where needed, WebAssembly. Our usage events do not include filenames, file contents, input text, chart values, raw errors, emails or license references. Network lookup tools (such as DNS, WHOIS, IP and speed tests) contact external services for their stated purpose. Loading the website, fonts, libraries and models also makes network requests. WebAssembly itself does not prevent network access.