font_preview 0.2.1

A package to inspect, compare and preview fonts that are being used in Flutter apps

font_preview

Inspect, compare, and preview fonts in your Flutter app across different sizes, weights, and styles.

Use it to visually check custom fonts, compare font families, and investigate missing font assets or synthesized bold and italic styles. Each preview displays the font family, size, style, and weight alongside your sample text.

Installation

flutter pub add font_preview

Use a regular dependency when importing the package from lib/. If you only use it in separate development tooling or tests, use flutter pub add --dev font_preview instead.

Preview a custom font

Register your font assets in your app's pubspec.yaml. The family name must match the name passed to FontProvider.fromFontFamily:

flutter:
  fonts:
    - family: Ubuntu
      fonts:
        - asset: assets/fonts/Ubuntu-Regular.ttf
          weight: 400
        - asset: assets/fonts/Ubuntu-Bold.ttf
          weight: 700

Replace these paths with your own font files. See the example configuration for additional weights and italic styles.

Import the package and call FontPreview.previewFonts from a context beneath a MaterialApp, such as a button in your home page:

import 'package:flutter/material.dart';
import 'package:font_preview/font_preview.dart';

class PreviewButton extends StatelessWidget {
  const PreviewButton({super.key});

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: () {
        FontPreview.previewFonts(
          context,
          previewText: 'Flutter is Great',
          fonts: [FontProvider.fromFontFamily('Ubuntu')],
          fontStyles: [FontStyle.normal],
          fontWeights: [FontWeight.w400, FontWeight.w700],
        );
      },
      child: const Text('Preview Ubuntu'),
    );
  }
}

The helper pushes a new route containing a scrollable preview list. It does not register or download font assets itself.

Compare fonts with google_fonts

Add google_fonts to your app if you want to use its font loaders:

flutter pub add google_fonts

In addition to the imports above, add:

import 'package:google_fonts/google_fonts.dart';

Wrap each font's style builder with FontProvider.fromBuilder, forwarding the requested size, weight, and style:

FontPreview.previewFonts(
  context,
  previewText: 'Flutter is Great',
  fonts: [
    FontProvider.fromFontFamily('Ubuntu'),
    FontProvider.fromBuilder(
      (fontSize, fontWeight, fontStyle) => GoogleFonts.raleway(
        fontSize: fontSize,
        fontWeight: fontWeight,
        fontStyle: fontStyle,
      ),
    ),
    FontProvider.fromBuilder(
      (fontSize, fontWeight, fontStyle) => GoogleFonts.roboto(
        fontSize: fontSize,
        fontWeight: fontWeight,
        fontStyle: fontStyle,
      ),
    ),
  ],
  fontStyles: [FontStyle.normal],
);

For each size, weight, and style combination, the fonts appear together in a vertically stacked comparison group. FontProvider.fromBuilder accepts any callback that returns a TextStyle, not just Google Fonts builders.

Font downloads and asset loading remain the responsibility of google_fonts or your own loader. Follow its setup instructions for bundled assets or runtime fetching.

Customize sizes, weights, and styles

FontPreview.previewFonts requires previewText and fonts. Its optional parameters default to:

Parameter	Default
previewSizes	[16.0] (kPreviewFontSizes)
fontWeights	All nine weights, FontWeight.w100 through FontWeight.w900
fontStyles	Normal and italic (FontStyle.values)

Every combination is previewed, ordered by size, then weight, then style. To limit the preview to specific variants:

FontPreview.previewFonts(
  context,
  previewText: 'Flutter is Great',
  fonts: [FontProvider.fromFontFamily('Ubuntu')],
  fontStyles: [FontStyle.normal, FontStyle.italic],
  fontWeights: [FontWeight.w400, FontWeight.w700],
  previewSizes: [11.0, 12.0, 14.0, 16.0, 18.0, 22.0],
);

Embed a preview in your own screen

Use FontPreviewList directly instead of opening a route. Unlike the navigation helper, its constructor requires all three variant lists:

Scaffold(
  appBar: AppBar(title: const Text('Font preview')),
  body: FontPreviewList(
    text: 'Flutter is Great',
    fonts: [FontProvider.fromFontFamily('Ubuntu')],
    previewSizes: kPreviewFontSizes,
    fontWeights: FontWeight.values,
    fontStyles: FontStyle.values,
  ),
);

The widget contains a ListView; give it bounded height, for example with Expanded when placing it inside a Column.

Recognize fallback rendering

The preview list sets the bundled BungeeShade-Regular font as its font-family fallback, replacing any fallback list supplied by your style builder. Its distinctive appearance helps reveal when the requested font cannot render your text:

This is a visual aid, not an automated font-loading check:

• Missing glyphs can trigger fallback even when the primary font is loaded.
• If neither font supports a glyph, Flutter may use another fallback.
• Missing weight or style assets may cause Flutter to select another face or synthesize a style rather than show Bungee Shade.
• Preview labels describe the requested TextStyle, not the actual font face used by the renderer.

Run the example

The example app demonstrates custom Ubuntu assets, Google Fonts, comparisons, and an intentionally unknown font family to show fallback rendering.

From a checkout of this repository:

cd example
flutter pub get
flutter run

See the changelog for release history.