How to Create Custom JSON Themes for Power BI (The 2026 Guide)

If you are still clicking on every single chart to change the font size from 10px to 12px, you are wasting hours of your life. It is time to learn the power of the JSON Theme file.

Power BI is an incredible tool, but its default styling often leaves a lot to be desired. By default, you get basic colors and small fonts. Most beginners try to fix this by manually formatting every visual. They click the paintbrush icon, scroll down, change the color, change the title size, and add a border.

Then they add a second chart... and do it all over again.

The professional way to handle design in Power BI is using a JSON Theme File. This is a simple text file that tells Power BI: "Hey, make every title 14px, make every background white, and use these specific brand colors."

The Magic: Once you import a JSON theme, it applies to every visual on every page instantly. It also sets the defaults for any future visuals you create.

The Anatomy of a Power BI Theme

A theme file is just a text file with the extension .json. It has three main sections you need to know about.

1. Name & Data Colors

This defines your color palette. Power BI will cycle through these colors for your bar charts, pie charts, and lines.

{ "name": "My Corporate Theme", "dataColors": [ "#0F4C81", "#53B6D9", "#F2C94C", "#F2994A", "#EB5757" ] }

2. Global Visual Styles

This is where you save time. Instead of targeting specific charts, you can target the "Universal" settings (marked by an asterisk *). This code snippet adds a border and rounded corners to every single visual in your report.

"visualStyles": { "*": { "*": { "border": [{ "show": true, "radius": 10, "color": "#E0E0E0" }], "title": [{ "show": true, "fontFamily": "Segoe UI Semibold", "fontSize": 14, "alignment": "center" }] } } }

3. Specific Visual Styles

Want your Cards to look different from your Charts? You can target them specifically. For example, making KPI Cards huge and bold:

"card": { "*": { "labels": [{ "fontSize": 30, "color": "#0F4C81" }], "categoryLabels": [{ "fontSize": 12, "color": "#828282" }] } }

How to Import Your Theme

Once you have written your code (or generated it using a tool):

1. Save the file as theme.json.
2. Open Power BI Desktop.
3. Go to the View tab on the Ribbon.
4. Click the Dropdown arrow next to the themes gallery.
5. Select Browse for themes.
6. Select your JSON file.

Boom. Your entire report transforms instantly.

Best Practices for 2026

In modern BI development, themes are not just about colors; they are about usability.

• Accessibility First: Ensure your `dataColors` have high contrast. Use a Color Blindness simulator to test your palette.
• Reduce Chart Junk: Use your theme to turn off background images and unnecessary gridlines globally.
• Standardize Fonts: Stick to standard web fonts (Segoe UI, Arial, DIN) to ensure your report renders correctly on all devices.

Conclusion

A JSON theme file is your "Brand Kit" for data. It ensures consistency across your team and saves you hundreds of clicks per report. If you are serious about Power BI, stop painting and start coding your design.

Download January Skills: Power BI JSON Templates