diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index a04e471..d9ba9dc 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -11,21 +11,25 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
-      - run: npm install --ignore-scripts --no-audit --no-fund
+      - uses: actions/checkout@v5
+      - uses: actions/setup-node@v5
+        with:
+          cache: "npm"
+          node-version: 22
+      - run: npm ci --ignore-scripts --no-audit --no-fund
       - run: npm test
 
   publish-npm:
     needs: test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v5
+      - uses: actions/setup-node@v5
         with:
-          cache: 'npm'
+          node-version: 22
+          cache: "npm"
           registry-url: https://registry.npmjs.org/
-      - run: npm install --ignore-scripts --no-audit --no-fund
+      - run: npm ci --ignore-scripts --no-audit --no-fund
       - run: npm run build
       - run: npm publish --public
         env:
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index adf4214..91ca824 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -14,11 +14,12 @@ jobs:
     name: Unit tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Use Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v5
         with:
           cache: "npm"
+          node-version: 22
       - run: npm install --ignore-scripts --no-audit --no-fund
       - run: npm test
 
@@ -26,11 +27,12 @@ jobs:
     name: Check types
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - name: Use Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v5
         with:
           cache: "npm"
+          node-version: 22
       - run: npm install --ignore-scripts --no-audit --no-fund
       - run: npm run check
 
@@ -39,11 +41,12 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Use Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v5
         with:
           cache: "npm"
+          node-version: 22
       - run: npm install --ignore-scripts --no-audit --no-fund
       - name: Build package
         run: npm run build
diff --git a/package.json b/package.json
index e5b7f6e..3790988 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,7 @@
     "default": "./dist/css-design-tokens.js"
   },
   "engines": {
-    "node": ">=18"
+    "node": ">=22"
   },
   "scripts": {
     "test": "vitest run",
diff --git a/src/destructure-line-height.test.ts b/src/destructure-line-height.test.ts
index a77ea53..cadd21a 100644
--- a/src/destructure-line-height.test.ts
+++ b/src/destructure-line-height.test.ts
@@ -22,6 +22,7 @@ test('percentage', () => {
 
 test('number', () => {
 	expect.soft(destructure_line_height('1')).toEqual(1)
+	expect.soft(destructure_line_height('1.0')).toEqual(1)
 	expect.soft(destructure_line_height('1.1')).toEqual(1.1)
 	expect.soft(destructure_line_height('1e2')).toEqual(100)
 })
@@ -36,6 +37,15 @@ test('length', () => {
 	expect.soft(destructure_line_height('1e2em')).toEqual({ value: 100, unit: 'em' })
 })
 
+test('zero', () => {
+	expect.soft(destructure_line_height('0%')).toEqual(0)
+	expect.soft(destructure_line_height('0.0%')).toEqual(0)
+	expect.soft(destructure_line_height('0px')).toEqual(0)
+	expect.soft(destructure_line_height('0.0px')).toEqual(0)
+	expect.soft(destructure_line_height('0')).toEqual(0)
+	expect.soft(destructure_line_height('0.0')).toEqual(0)
+})
+
 test('unprocessable values', () => {
 	expect.soft(destructure_line_height('var(--my-line-height)')).toEqual(null)
 	expect.soft(destructure_line_height('var(--my-line-height, 1.2)')).toEqual(null)
diff --git a/src/destructure-line-height.ts b/src/destructure-line-height.ts
index d695f21..c7e9425 100644
--- a/src/destructure-line-height.ts
+++ b/src/destructure-line-height.ts
@@ -21,8 +21,12 @@ export function destructure_line_height(value: string): Length | number | null {
 
 	switch (maybe_dimension.type) {
 		case 'Dimension': {
+			let value = Number(maybe_dimension.value)
+			if (value === 0) {
+				return 0
+			}
 			return {
-				value: Number(maybe_dimension.value),
+				value,
 				unit: maybe_dimension.unit
 			}
 		}
diff --git a/src/index.test.ts b/src/index.test.ts
index 740f5b3..114aa12 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -17,7 +17,7 @@ describe('analysis_to_tokens', () => {
 
 	let expected = {
 		color: {
-			'green-5e0cf03': {
+			'green-3fc58faf': {
 				$type: 'color',
 				$value: {
 					colorSpace: 'srgb',
@@ -85,7 +85,7 @@ describe('css_to_tokens', () => {
 			}
 		`)
 			expect(actual.color).toEqual({
-				'green-5e0cf03': {
+				'green-3fc58faf': {
 					$type: 'color',
 					$value: {
 						colorSpace: 'srgb',
@@ -98,7 +98,7 @@ describe('css_to_tokens', () => {
 						[EXTENSION_CSS_PROPERTIES]: ['color', 'border-color'],
 					}
 				},
-				'grey-8139d9b': {
+				'grey-d68e53e4': {
 					$type: 'color',
 					$value: {
 						colorSpace: 'srgb',
@@ -130,7 +130,7 @@ describe('css_to_tokens', () => {
 			}
 		`)
 			expect(actual.color).toEqual({
-				'black-991c5d52': {
+				'black-edec3e7a': {
 					$type: 'color',
 					$value: {
 						colorSpace: 'srgb',
@@ -159,9 +159,52 @@ describe('css_to_tokens', () => {
 		test('extensions[css-properties] does not yield a type error', () => {
 			let actual = css_to_tokens('a { color: green; }')
 			// Not so much interested in the test result, more looking that this isn't giving a type error
-			let properties = actual.color['green-5e0cf03']!['$extensions'][EXTENSION_CSS_PROPERTIES]
+			let properties = actual.color['green-3fc58faf']!['$extensions'][EXTENSION_CSS_PROPERTIES]
 			expect(properties).toEqual(['color'])
 		})
+
+		test('deduplicates colors', () => {
+			let actual = css_to_tokens(`
+				.my-design-system {
+					color: green;
+					border-color: rgb(0, 128, 0);
+					background-color: #008000;
+					color: #008000;
+				}
+				.alpha {
+					border-color: rgb(0 128 0 / 0.5);
+					border-color: rgb(0 128 0 / .5);
+				}
+		`)
+			expect(actual.color).toEqual({
+				'green-3fc58faf': {
+					$type: 'color',
+					$value: {
+						colorSpace: 'srgb',
+						components: [0, 0.5019607843137255, 0],
+						alpha: 1,
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: 'green',
+						[EXTENSION_USAGE_COUNT]: 4,
+						[EXTENSION_CSS_PROPERTIES]: ['color', 'border-color', 'background-color'],
+					}
+				},
+				'green-64a061f5': {
+					$type: 'color',
+					$value: {
+						colorSpace: 'srgb',
+						components: [0, 0.5019607843137255, 0],
+						alpha: 0.5,
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: 'rgb(0 128 0 / 0.5)',
+						[EXTENSION_USAGE_COUNT]: 2,
+						[EXTENSION_CSS_PROPERTIES]: ['border-color'],
+					}
+				},
+			})
+		})
 	})
 
 	describe('font sizes', () => {
@@ -185,6 +228,26 @@ describe('css_to_tokens', () => {
 				},
 			})
 		})
+		test('handles `0`', () => {
+			let actual = css_to_tokens(`
+			.my-design-system {
+				font-size: 0;
+			}
+		`)
+			expect(actual.font_size).toEqual({
+				'fontSize-c238': {
+					$type: 'dimension',
+					$value: {
+						value: 0,
+						unit: 'px'
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '0',
+						[EXTENSION_USAGE_COUNT]: 1,
+					}
+				},
+			})
+		})
 
 		test('outputs a value type when not using rem or px', () => {
 			let actual = css_to_tokens(`
@@ -236,6 +299,57 @@ describe('css_to_tokens', () => {
 				},
 			})
 		})
+
+		test('dedupes identical sizes', () => {
+			let actual = css_to_tokens(`
+			.my-design-system {
+				font-size: 16px;
+				font-size: 16.0PX;
+
+				font-size: 0.5rem;
+				font-size: .5rem;
+
+				font-size: 0;
+				font-size: 0px;
+				font-size: 0rem;
+			}
+		`)
+			expect(actual.font_size).toEqual({
+				'fontSize-171eed': {
+					$type: 'dimension',
+					$value: {
+						value: 16,
+						unit: 'px'
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '16px',
+						[EXTENSION_USAGE_COUNT]: 2,
+					}
+				},
+				'fontSize-548aa743': {
+					$type: 'dimension',
+					$value: {
+						unit: 'rem',
+						value: 0.5,
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '0.5rem',
+						[EXTENSION_USAGE_COUNT]: 2,
+					},
+				},
+				'fontSize-c238': {
+					$type: 'dimension',
+					$value: {
+						unit: 'px',
+						value: 0,
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '0',
+						[EXTENSION_USAGE_COUNT]: 3,
+					},
+				},
+			})
+		})
 	})
 
 	describe('font families', () => {
@@ -280,6 +394,64 @@ describe('css_to_tokens', () => {
 			})
 		})
 
+		test('dedupes line heights', () => {
+			let actual = css_to_tokens(`
+				.my-design-system {
+					line-height: 1;
+					line-height: 1.0;
+
+					line-height: 1rem;
+					line-height: 1.0rem;
+
+					line-height: 1px;
+					line-height: 1.0px;
+
+					line-height: 0;
+					line-height: 0.0;
+				}
+			`)
+			expect(actual.line_height).toEqual({
+				'lineHeight-31': {
+					$type: 'number',
+					$value: 1,
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '1',
+						[EXTENSION_USAGE_COUNT]: 2,
+					}
+				},
+				'lineHeight-17fec9': {
+					$type: 'dimension',
+					$value: {
+						value: 1,
+						unit: 'rem'
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '1rem',
+						[EXTENSION_USAGE_COUNT]: 2,
+					}
+				},
+				'lineHeight-c5f9': {
+					$type: 'dimension',
+					$value: {
+						value: 1,
+						unit: 'px'
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '1px',
+						[EXTENSION_USAGE_COUNT]: 2,
+					}
+				},
+				'lineHeight-30': {
+					$type: 'number',
+					$value: 0,
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '0',
+						[EXTENSION_USAGE_COUNT]: 2,
+					}
+				},
+			})
+		})
+
 		test('outputs a number type when using a number', () => {
 			let actual = css_to_tokens(`
 			.my-design-system {
@@ -467,10 +639,10 @@ describe('css_to_tokens', () => {
 	describe('duration', () => {
 		test('outputs a token when using a valid duration', () => {
 			let actual = css_to_tokens(`
-			.my-design-system {
-				animation-duration: 1s;
-			}
-		`)
+				.my-design-system {
+					animation-duration: 1s;
+				}
+			`)
 			expect(actual.duration).toEqual({
 				'duration-17005f': {
 					$type: 'duration',
@@ -488,12 +660,12 @@ describe('css_to_tokens', () => {
 
 		test('outputs an unparsed token when using an invalid duration', () => {
 			let actual = css_to_tokens(`
-			.my-design-system {
-				animation-duration: var(--test);
-			}
-		`)
+				.my-design-system {
+					animation-duration: var(--test);
+				}
+			`)
 			expect(actual.duration).toEqual({
-				'duration-452f2b3b': {
+				'duration-f9e24f32': {
 					$value: 'var(--test)',
 					$extensions: {
 						[EXTENSION_AUTHORED_AS]: 'var(--test)',
@@ -502,6 +674,43 @@ describe('css_to_tokens', () => {
 				},
 			})
 		})
+
+		test('dedupes values', () => {
+			let actual = css_to_tokens(`
+				.my-design-system {
+					animation-duration: 100ms;
+					animation-duration: 0.1s;
+					animation-duration: .1s;
+
+					animation-duration: 1S;
+					animation-duration: 1000MS;
+				}
+			`)
+			expect(actual.duration).toEqual({
+				'duration-bdf1': {
+					$type: 'duration',
+					$value: {
+						value: 100,
+						unit: 'ms'
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '100ms',
+						[EXTENSION_USAGE_COUNT]: 3,
+					}
+				},
+				'duration-17005f': {
+					$type: 'duration',
+					$value: {
+						value: 1000,
+						unit: 'ms'
+					},
+					$extensions: {
+						[EXTENSION_AUTHORED_AS]: '1S',
+						[EXTENSION_USAGE_COUNT]: 2,
+					}
+				},
+			})
+		})
 	})
 
 	describe('easing', () => {
diff --git a/src/index.ts b/src/index.ts
index ba928ab..d6595e4 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -93,25 +93,37 @@ export function analysis_to_tokens(analysis: CssAnalysis): Tokens {
 			for (let [group, group_colors] of color_groups) {
 				for (let color of group_colors) {
 					let color_token = color_to_token(color)
+					let count = get_count(unique[color]!)
 
 					if (color_token !== null) {
-						let name = `${color_dict.get(group)}-${hash(color)}`
+						let { colorSpace, components, alpha } = color_token
+						let name = `${color_dict.get(group)}-${hash([colorSpace, ...components, alpha].join(''))}`
 
 						let items_per_context = analysis.values.colors.itemsPerContext as ItemsPerContext
-						let properties = Object.entries(items_per_context).reduce((acc, [property, collection]) => {
-							if (color in collection.unique || (collection.uniqueWithLocations && color in collection.uniqueWithLocations)) {
-								acc.push(property)
+						let new_properties = Object.entries(items_per_context).reduce((acc, [property, collection]) => {
+							if (color in collection.unique) {
+								return acc.add(property)
+							}
+							if (collection.uniqueWithLocations && color in collection.uniqueWithLocations) {
+								return acc.add(property)
 							}
 							return acc
-						}, [] as Array<string>)
+						}, new Set() as Set<string>)
 
-						colors[name] = {
-							$type: 'color',
-							$value: color_token,
-							$extensions: {
-								[EXTENSION_AUTHORED_AS]: color,
-								[EXTENSION_USAGE_COUNT]: get_count(unique[color]!),
-								[EXTENSION_CSS_PROPERTIES]: properties,
+						if (colors[name]) {
+							let old_properties = colors[name].$extensions[EXTENSION_CSS_PROPERTIES]
+							colors[name].$extensions[EXTENSION_CSS_PROPERTIES] = Array.from(new Set(old_properties).union(new_properties))
+							colors[name].$extensions[EXTENSION_USAGE_COUNT] += count
+						}
+						else {
+							colors[name] = {
+								$type: 'color',
+								$value: color_token,
+								$extensions: {
+									[EXTENSION_AUTHORED_AS]: color,
+									[EXTENSION_USAGE_COUNT]: count,
+									[EXTENSION_CSS_PROPERTIES]: Array.from(new_properties),
+								}
 							}
 						}
 					}
@@ -124,7 +136,6 @@ export function analysis_to_tokens(analysis: CssAnalysis): Tokens {
 			let unique = get_unique(analysis.values.fontSizes)
 
 			for (let font_size in unique) {
-				let name = `fontSize-${hash(font_size)}`
 				let parsed = parse_length(font_size)
 				let extensions = {
 					[EXTENSION_AUTHORED_AS]: font_size,
@@ -132,15 +143,23 @@ export function analysis_to_tokens(analysis: CssAnalysis): Tokens {
 				}
 
 				if (parsed === null) {
+					let name = `fontSize-${hash(font_size)}`
 					font_sizes[name] = {
 						$value: font_size,
 						$extensions: extensions,
 					}
-				} else {
-					font_sizes[name] = {
-						$type: 'dimension',
-						$value: parsed,
-						$extensions: extensions,
+				}
+				else {
+					let name = `fontSize-${hash(parsed.value.toString() + parsed.unit)}`
+					if (font_sizes[name]) {
+						font_sizes[name].$extensions[EXTENSION_USAGE_COUNT] += extensions[EXTENSION_USAGE_COUNT]
+					}
+					else {
+						font_sizes[name] = {
+							$type: 'dimension',
+							$value: parsed,
+							$extensions: extensions,
+						}
 					}
 				}
 			}
@@ -169,7 +188,6 @@ export function analysis_to_tokens(analysis: CssAnalysis): Tokens {
 			let unique = get_unique(analysis.values.lineHeights)
 
 			for (let line_height in unique) {
-				let name = `lineHeight-${hash(line_height)}`
 				let parsed = destructure_line_height(line_height)
 				let extensions = {
 					[EXTENSION_AUTHORED_AS]: line_height,
@@ -177,24 +195,41 @@ export function analysis_to_tokens(analysis: CssAnalysis): Tokens {
 				}
 
 				if (parsed === null) {
+					let name = `lineHeight-${hash(line_height)}`
 					line_heights[name] = {
 						$value: line_height,
 						$extensions: extensions,
 					}
-				} else if (typeof parsed === 'number') {
-					line_heights[name] = {
-						$type: 'number',
-						$value: parsed,
-						$extensions: extensions,
+				}
+				else if (typeof parsed === 'number') {
+					let name = `lineHeight-${hash(parsed)}`
+					if (line_heights[name]) {
+						line_heights[name].$extensions[EXTENSION_USAGE_COUNT] += extensions[EXTENSION_USAGE_COUNT]
 					}
-				} else if (typeof parsed === 'object') {
-					if (parsed.unit === 'px' || parsed.unit === 'rem') {
+					else {
 						line_heights[name] = {
-							$type: 'dimension',
+							$type: 'number',
 							$value: parsed,
 							$extensions: extensions,
 						}
-					} else {
+					}
+				}
+				else if (typeof parsed === 'object') {
+					if (parsed.unit === 'px' || parsed.unit === 'rem') {
+						let name = `lineHeight-${hash(parsed.value.toString() + parsed.unit)}`
+						if (line_heights[name]) {
+							line_heights[name].$extensions[EXTENSION_USAGE_COUNT] += extensions[EXTENSION_USAGE_COUNT]
+						}
+						else {
+							line_heights[name] = {
+								$type: 'dimension',
+								$value: parsed,
+								$extensions: extensions,
+							}
+						}
+					}
+					else {
+						let name = `lineHeight-${hash(line_height)}`
 						line_heights[name] = {
 							$value: line_height,
 							$extensions: extensions,
@@ -269,23 +304,29 @@ export function analysis_to_tokens(analysis: CssAnalysis): Tokens {
 			for (let duration in unique) {
 				let parsed = convert_duration(duration)
 				let is_valid = parsed < Number.MAX_SAFE_INTEGER - 1
-				let name = hash(parsed.toString())
 				let extensions = {
 					[EXTENSION_AUTHORED_AS]: duration,
 					[EXTENSION_USAGE_COUNT]: get_count(unique[duration]!),
 				}
 
 				if (is_valid) {
-					durations[`duration-${name}`] = {
-						$type: 'duration',
-						$value: {
-							value: parsed,
-							unit: 'ms'
-						},
-						$extensions: extensions,
+					let name = `duration-${hash(parsed.toString())}`
+					if (durations[name]) {
+						durations[name].$extensions[EXTENSION_USAGE_COUNT] += extensions[EXTENSION_USAGE_COUNT]
+					}
+					else {
+						durations[name] = {
+							$type: 'duration',
+							$value: {
+								value: parsed,
+								unit: 'ms'
+							},
+							$extensions: extensions,
+						}
 					}
 				} else {
-					durations[`duration-${name}`] = {
+					let name = `duration-${hash('invalid' + parsed.toString())}`
+					durations[name] = {
 						$value: duration,
 						$extensions: extensions,
 					}
diff --git a/src/parse-length.test.ts b/src/parse-length.test.ts
index 681fcd0..57eb91f 100644
--- a/src/parse-length.test.ts
+++ b/src/parse-length.test.ts
@@ -26,6 +26,12 @@ test('absolute size keywords', () => {
 	expect.soft(parse_length('xxx-large')).toEqual({ value: 3, unit: 'rem' })
 })
 
+test('unitless 0', () => {
+	expect.soft(parse_length('0')).toEqual({ value: 0, unit: 'px' })
+	expect.soft(parse_length('0.0')).toEqual({ value: 0, unit: 'px' })
+	expect.soft(parse_length('+0')).toEqual({ value: 0, unit: 'px' })
+})
+
 test('invalid values', () => {
 	expect.soft(parse_length('')).toBeNull()
 	expect.soft(parse_length('1')).toBeNull()
diff --git a/src/parse-length.ts b/src/parse-length.ts
index ef40c26..1431f0c 100644
--- a/src/parse-length.ts
+++ b/src/parse-length.ts
@@ -32,10 +32,19 @@ export function parse_length(value: string): DesignTokenLength | null {
 
 	switch (maybe_length.type) {
 		case 'Dimension': {
-			if (maybe_length.unit === 'px' || maybe_length.unit === 'rem') {
+			let unit = maybe_length.unit.toLowerCase()
+			if (unit === 'px' || unit === 'rem') {
+				let value = Number(maybe_length.value)
+				// Always return `0px`, `0`, or `0rem` as `0px`
+				if (value === 0) {
+					return {
+						value: 0,
+						unit: 'px',
+					}
+				}
 				return {
-					value: Number(maybe_length.value),
-					unit: maybe_length.unit
+					value: value,
+					unit,
 				}
 			}
 			break
@@ -51,6 +60,16 @@ export function parse_length(value: string): DesignTokenLength | null {
 					unit: 'rem'
 				}
 			}
+			break
+		}
+		case 'Number': {
+			if (Number(maybe_length.value) === 0) {
+				return {
+					value: 0,
+					unit: 'px',
+				}
+			}
+			break
 		}
 	}
 
diff --git a/tsconfig.json b/tsconfig.json
index 59e2b2c..b7c8dd9 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -2,7 +2,7 @@
 	"compilerOptions": {
 		// Base options:
 		"skipLibCheck": true,
-		"target": "es2022",
+		"target": "esnext",
 		"verbatimModuleSyntax": true,
 		"allowJs": true,
 		"checkJs": true,
@@ -15,11 +15,8 @@
 		"moduleResolution": "bundler",
 		"allowSyntheticDefaultImports": true,
 		"noEmit": true,
-		// Code runs in the DOM
 		"lib": [
-			"ES2022",
-			"DOM",
-			"DOM.Iterable"
+			"esnext",
 		],
 	},
 	"include": [