Flatfile supports modifying most UI elements including colors, fonts, borders, padding, and more via the Space endpoint.
  1. Start by simply updating theme.root.primaryColor and theme.sidebar.logo when calling spaces.update().
  2. If needed, you can customize the theme further with additional css variables.

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Building a theme

Learn how to create a Space with a theme, and update a theme from an Event listener. 
import api from "@flatfile/api";

export default function flatfileEventListener(listener) {
  //listen for space:configure job and build out space
  listener.filter({ job: "space:configure" }, (configure) => {});

  //theme during creation or update your space after it is created
  listener.on("space:created", async ({ context: { spaceId } }) => {
    const updateSpace = await api.spaces.update(spaceId, {
      metadata: {
        theme: {
          root: {
            primaryColor: "red",
          },
          sidebar: {
            logo: "https://image.png",
          },
          // See reference for all possible variables
        },
      },
    });
  });
}
See full code example in our flatfile-docs-kitchen-sink Github repo

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Theme reference

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theme.root

Theme root configuration example
The sidebar, table and document will automatically inherit theming from your root variables!

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Font

fontFamily string
The font family used throughout the application. Only system fonts are supported at the moment

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Colors

primaryColor string
The primary color used throughout the application. dangerColor string
The color used for error messages. warningColor string
The color used for warning messages. borderColor string
The color used for borders throughout the application.

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theme.sidebar

Theme sidebar configuration example
You can override the default colors of the sidebar below. If these are not set they will inherit from your root colors.
logo string
The img path for the logo displayed in the sidebar. textColor string
The color of the text in the sidebar. titleColor string
The color of the title in the sidebar. focusBgColor string
The background color of the active navigation link. The hover state will use the same color with 30% opacity applied. focusTextColor string
The text color of the active/focused navigation link. backgroundColor string
The background color of the sidebar.

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theme.table

Theme table configuration example
You can override the default colors and values for different elements in the table below. If these are not set they will inherit from your root values.

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Font

fontFamily string
The font family used throughout the table. Only system fonts are supported at the moment

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Active cell

cell.active.borderWidth string
The width of the border around the active cell. cell.active.borderShadow string
The box shadow around the active cell. cell.number.fontFamily string
The font family for number cells.

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Column header

Theme table column configuration column.header.backgroundColor string
The background color of the column headers in the table. column.header.color string
The text color of the column headers in the table.

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Index column

Theme table index column configuration indexColumn.backgroundColor string
The background color of the first column in the table. indexColumn.color string
The text color of the first column in the table. indexColumn.selected.backgroundColor string
The background color of the first column in the table when selected.

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Checkboxes

Theme table inputs configuration inputs.checkbox.color string
The color of the checkboxes in the table. inputs.checkbox.borderColor string
The color of the border for the checkboxes in the table.

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Filters

filters.outerBorderRadius string
The border radius of the table filters filters.innerBorderRadius string
The border radius for the individual filters filters.outerBorder string
The border of the table filters. By default there is no border.
When nested objects share the same border radius, small gaps may appear. To resolve this, adjust the inner and outer border radius on the filters to seamlessly fill any gaps.

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Buttons

buttons.iconColor string
The color of the icon buttons in the toolbar and table buttons.pill.color string
The color of the pill buttons in the toolbar

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theme.email

You can theme the guest invite emails as well as guest email verification emails via the properties below. These are sent to a guest when they are invited to a Space via the guest management page in your Space.
Email theming is only available on the pro and enterprise plans.
logo string
The URL of the image displayed at the top of the email textColor string
The color of the text in the email titleColor string
The color of the title in the email buttonBgColor string
The background color of the button buttonTextColor string
The text color of the button footerTextColor string
The text color of the footer text backgroundColor string
The background color of the email

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theme.email.dark

If your default email theme (as set above) is light, we suggest adding a dark mode email theme. Different email providers handle dark and light mode differently. While Apple Mail and some other clients will respect dark mode variables, some email providers do not support dark mode and will display your default theme. We suggest you test your themes across various email clients before going to production to ensure consistent appearance. logo string
The URL of the image displayed at the top of the email in dark mode textColor string
The color of the text in the email in dark mode titleColor string
The color of the title in the email in dark mode buttonBgColor string
The background color of the button in dark mode buttonTextColor string
The text color of the button in dark mode footerTextColor string
The text color of the footer text in dark mode backgroundColor string
The background color of the email in dark mode

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Deprecation Notice

Flatfile’s new design system released in Q1 2025 supports a more streamlined experience when configuring theme. The new system accepts a more limited set of properties, but ensures those supplied properties are cohesively applied across the application. As a result, many of the original theme.root properties which applied to specific UI elements have been deprecated. We have taken steps to ensure some level of backwards compatibility for these properties in the new system - however we recommend any usage of these properties be updated to the new system as soon as possible.

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Example Project

Find the theming example in the Flatfile GitHub repository.