diff --git a/src/lib/index.ts b/src/lib/index.ts
index 5d3ef74..5fce82d 100644
--- a/src/lib/index.ts
+++ b/src/lib/index.ts
@@ -583,3 +583,59 @@ export function format(
 export function minify(css: string): string {
 	return format(css, { minify: true })
 }
+
+export const LINE_TYPE_SELECTOR = 1
+export const LINE_TYPE_DECLARATION = 2
+export const LINE_TYPE_BRACKET = 3
+export const LINE_TYPE_ATRULE = 4
+export const LINE_TYPE_COMMENT = 5
+export const LINE_TYPE_EMPTY = 6
+
+export type LineType =
+	| typeof LINE_TYPE_SELECTOR
+	| typeof LINE_TYPE_DECLARATION
+	| typeof LINE_TYPE_BRACKET
+	| typeof LINE_TYPE_ATRULE
+	| typeof LINE_TYPE_COMMENT
+	| typeof LINE_TYPE_EMPTY
+
+function classify_lines(lines: string[]): LineType[] {
+	let types: LineType[] = []
+	let in_multiline_comment = false
+
+	for (let line of lines) {
+		let trimmed = line.trimEnd()
+
+		if (in_multiline_comment) {
+			types.push(LINE_TYPE_COMMENT)
+			if (trimmed.includes('*/')) in_multiline_comment = false
+			continue
+		}
+
+		if (trimmed === '') {
+			types.push(LINE_TYPE_EMPTY)
+		} else if (trimmed.trimStart().startsWith('/*')) {
+			types.push(LINE_TYPE_COMMENT)
+			if (!trimmed.slice(trimmed.indexOf('/*') + 2).includes('*/')) in_multiline_comment = true
+		} else if (trimmed.endsWith(CLOSE_BRACE)) {
+			types.push(LINE_TYPE_BRACKET)
+		} else if (trimmed.trimStart().startsWith('@')) {
+			types.push(LINE_TYPE_ATRULE)
+		} else if (trimmed.endsWith(OPEN_BRACE) || trimmed.endsWith(COMMA)) {
+			types.push(LINE_TYPE_SELECTOR)
+		} else {
+			types.push(LINE_TYPE_DECLARATION)
+		}
+	}
+
+	return types
+}
+
+export function format_with_types(
+	css: string,
+	options: Omit<FormatOptions, 'minify'> = Object.create(null),
+): { css: string; types: LineType[] } {
+	let formatted = format(css, options)
+	let types = classify_lines(formatted.split('\n'))
+	return { css: formatted, types }
+}
diff --git a/test/format-with-types.test.ts b/test/format-with-types.test.ts
new file mode 100644
index 0000000..5e2390e
--- /dev/null
+++ b/test/format-with-types.test.ts
@@ -0,0 +1,156 @@
+import { describe, test, expect } from 'vitest'
+import {
+	format_with_types,
+	LINE_TYPE_SELECTOR,
+	LINE_TYPE_DECLARATION,
+	LINE_TYPE_BRACKET,
+	LINE_TYPE_ATRULE,
+	LINE_TYPE_COMMENT,
+	LINE_TYPE_EMPTY,
+} from '../src/lib/index.js'
+
+describe('format_with_types', () => {
+	test('simple rule', () => {
+		let { css, types } = format_with_types('a { color: red; }')
+		expect(css).toBe('a {\n\tcolor: red;\n}')
+		expect(types).toEqual([LINE_TYPE_SELECTOR, LINE_TYPE_DECLARATION, LINE_TYPE_BRACKET])
+	})
+
+	test('multiple declarations', () => {
+		let { css, types } = format_with_types('a { color: red; background: blue; }')
+		expect(types).toEqual([
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('multi-line selector list', () => {
+		let { css, types } = format_with_types('a, b { color: red; }')
+		expect(css).toBe('a,\nb {\n\tcolor: red;\n}')
+		expect(types).toEqual([
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('atrule with block', () => {
+		let { css, types } = format_with_types('@media all { a { color: red } }')
+		expect(css).toBe('@media all {\n\ta {\n\t\tcolor: red;\n\t}\n}')
+		expect(types).toEqual([
+			LINE_TYPE_ATRULE,
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('atrule without block (@charset)', () => {
+		let { css, types } = format_with_types('@charset "utf-8";')
+		expect(css).toBe('@charset "utf-8";')
+		expect(types).toEqual([LINE_TYPE_ATRULE])
+	})
+
+	test('atrule without block (@import)', () => {
+		let { css, types } = format_with_types('@import "foo.css";')
+		expect(css).toBe('@import "foo.css";')
+		expect(types).toEqual([LINE_TYPE_ATRULE])
+	})
+
+	test('empty line between rules', () => {
+		let { css, types } = format_with_types('a {} b {}')
+		expect(css).toBe('a {}\n\nb {}')
+		expect(types).toEqual([LINE_TYPE_BRACKET, LINE_TYPE_EMPTY, LINE_TYPE_BRACKET])
+	})
+
+	test('single-line comment before rule', () => {
+		let { css, types } = format_with_types('/* comment */ a { color: red; }')
+		expect(css).toBe('/* comment */\na {\n\tcolor: red;\n}')
+		expect(types).toEqual([
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('single-line comment inside rule', () => {
+		let { css, types } = format_with_types('a { /* comment */ color: red; }')
+		expect(css).toBe('a {\n\t/* comment */\n\tcolor: red;\n}')
+		expect(types).toEqual([
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('multiline comment before rule', () => {
+		let { css, types } = format_with_types('/* line 1\n   line 2 */ a { color: red; }')
+		expect(css).toBe('/* line 1\n   line 2 */\na {\n\tcolor: red;\n}')
+		expect(types).toEqual([
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('multiline comment inside rule', () => {
+		let { css, types } = format_with_types(
+			'a {\n\t/* line 1\n\t   line 2 */\n\tcolor: red;\n}',
+		)
+		expect(css).toBe('a {\n\t/* line 1\n\t   line 2 */\n\tcolor: red;\n}')
+		expect(types).toEqual([
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('multiline comment spanning three lines', () => {
+		let { css, types } = format_with_types('/* a\n * b\n * c */ a { color: red; }')
+		expect(css).toBe('/* a\n * b\n * c */\na {\n\tcolor: red;\n}')
+		expect(types).toEqual([
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('comment containing a semicolon is not a declaration', () => {
+		let { css, types } = format_with_types('a { /* color: red; */ color: blue; }')
+		expect(types).toEqual([
+			LINE_TYPE_SELECTOR,
+			LINE_TYPE_COMMENT,
+			LINE_TYPE_DECLARATION,
+			LINE_TYPE_BRACKET,
+		])
+	})
+
+	test('comment containing a brace is not a bracket', () => {
+		let { css, types } = format_with_types('/* } */ a { color: red; }')
+		expect(types[0]).toBe(LINE_TYPE_COMMENT)
+	})
+
+	test('types array length matches number of lines', () => {
+		let input = '@media all { a, b { color: red; background: blue; } }'
+		let { css, types } = format_with_types(input)
+		expect(types).toHaveLength(css.split('\n').length)
+	})
+
+	test('tab_size option is forwarded', () => {
+		let { css } = format_with_types('a { color: red; }', { tab_size: 2 })
+		expect(css).toBe('a {\n  color: red;\n}')
+	})
+})