diff --git a/README.md b/README.md
index efc381a..b5035bf 100644
--- a/README.md
+++ b/README.md
@@ -473,10 +473,12 @@ Command-line tool for converting between JSON and TOON formats.
 ### Usage
 
 ```bash
-npx @toon-format/cli <input> [options]
+npx @toon-format/cli [options] [input]
 ```
 
-**Auto-detection:** The CLI automatically detects the operation based on file extension (`.json` → encode, `.toon` → decode).
+**Standard input:** Omit the input argument or use `-` to read from stdin. This enables piping data directly from other commands.
+
+**Auto-detection:** The CLI automatically detects the operation based on file extension (`.json` → encode, `.toon` → decode). When reading from stdin, use `--encode` or `--decode` flags to specify the operation (defaults to encode).
 
 ```bash
 # Encode JSON to TOON (auto-detected)
@@ -487,6 +489,16 @@ npx @toon-format/cli data.toon -o output.json
 
 # Output to stdout
 npx @toon-format/cli input.json
+
+# Pipe from stdin (no argument needed)
+cat data.json | npx @toon-format/cli
+echo '{"name": "Ada"}' | npx @toon-format/cli
+
+# Explicit stdin with hyphen (equivalent to above)
+cat data.json | npx @toon-format/cli -
+
+# Decode from stdin
+cat data.toon | npx @toon-format/cli --decode
 ```
 
 ### Options
@@ -516,6 +528,10 @@ npx @toon-format/cli data.json --delimiter "|" --length-marker -o output.toon
 
 # Lenient decoding (skip validation)
 npx @toon-format/cli data.toon --no-strict -o output.json
+
+# Stdin workflows
+echo '{"name": "Ada", "age": 30}' | npx @toon-format/cli --stats
+cat large-dataset.json | npx @toon-format/cli --delimiter "\t" > output.toon
 ```
 
 ## Format Overview
diff --git a/packages/cli/src/conversion.ts b/packages/cli/src/conversion.ts
new file mode 100644
index 0000000..228ab33
--- /dev/null
+++ b/packages/cli/src/conversion.ts
@@ -0,0 +1,90 @@
+import type { DecodeOptions, Delimiter, EncodeOptions } from '../../toon/src'
+import type { InputSource } from './types'
+import * as fsp from 'node:fs/promises'
+import * as path from 'node:path'
+import process from 'node:process'
+import { consola } from 'consola'
+import { estimateTokenCount } from 'tokenx'
+import { decode, encode } from '../../toon/src'
+import { formatInputLabel, readInput } from './utils'
+
+export async function encodeToToon(config: {
+  input: InputSource
+  output?: string
+  delimiter: Delimiter
+  indent: number
+  lengthMarker: NonNullable<EncodeOptions['lengthMarker']>
+  printStats: boolean
+}): Promise<void> {
+  const jsonContent = await readInput(config.input)
+
+  let data: unknown
+  try {
+    data = JSON.parse(jsonContent)
+  }
+  catch (error) {
+    throw new Error(`Failed to parse JSON: ${error instanceof Error ? error.message : String(error)}`)
+  }
+
+  const encodeOptions: EncodeOptions = {
+    delimiter: config.delimiter,
+    indent: config.indent,
+    lengthMarker: config.lengthMarker,
+  }
+
+  const toonOutput = encode(data, encodeOptions)
+
+  if (config.output) {
+    await fsp.writeFile(config.output, toonOutput, 'utf-8')
+    const relativeInputPath = formatInputLabel(config.input)
+    const relativeOutputPath = path.relative(process.cwd(), config.output)
+    consola.success(`Encoded \`${relativeInputPath}\` → \`${relativeOutputPath}\``)
+  }
+  else {
+    console.log(toonOutput)
+  }
+
+  if (config.printStats) {
+    const jsonTokens = estimateTokenCount(jsonContent)
+    const toonTokens = estimateTokenCount(toonOutput)
+    const diff = jsonTokens - toonTokens
+    const percent = ((diff / jsonTokens) * 100).toFixed(1)
+
+    console.log()
+    consola.info(`Token estimates: ~${jsonTokens} (JSON) → ~${toonTokens} (TOON)`)
+    consola.success(`Saved ~${diff} tokens (-${percent}%)`)
+  }
+}
+
+export async function decodeToJson(config: {
+  input: InputSource
+  output?: string
+  indent: number
+  strict: boolean
+}): Promise<void> {
+  const toonContent = await readInput(config.input)
+
+  let data: unknown
+  try {
+    const decodeOptions: DecodeOptions = {
+      indent: config.indent,
+      strict: config.strict,
+    }
+    data = decode(toonContent, decodeOptions)
+  }
+  catch (error) {
+    throw new Error(`Failed to decode TOON: ${error instanceof Error ? error.message : String(error)}`)
+  }
+
+  const jsonOutput = JSON.stringify(data, undefined, config.indent)
+
+  if (config.output) {
+    await fsp.writeFile(config.output, jsonOutput, 'utf-8')
+    const relativeInputPath = formatInputLabel(config.input)
+    const relativeOutputPath = path.relative(process.cwd(), config.output)
+    consola.success(`Decoded \`${relativeInputPath}\` → \`${relativeOutputPath}\``)
+  }
+  else {
+    console.log(jsonOutput)
+  }
+}
diff --git a/packages/cli/src/index.ts b/packages/cli/src/index.ts
index c791d7d..f7a25df 100644
--- a/packages/cli/src/index.ts
+++ b/packages/cli/src/index.ts
@@ -1,12 +1,13 @@
-import type { DecodeOptions, Delimiter, EncodeOptions } from '../../toon/src'
-import * as fsp from 'node:fs/promises'
+import type { Delimiter } from '../../toon/src'
+import type { InputSource } from './types'
 import * as path from 'node:path'
 import process from 'node:process'
 import { defineCommand, runMain } from 'citty'
 import { consola } from 'consola'
-import { estimateTokenCount } from 'tokenx'
 import { name, version } from '../../toon/package.json' with { type: 'json' }
-import { decode, DEFAULT_DELIMITER, DELIMITERS, encode } from '../../toon/src'
+import { DEFAULT_DELIMITER, DELIMITERS } from '../../toon/src'
+import { decodeToJson, encodeToToon } from './conversion'
+import { detectMode } from './utils'
 
 const main = defineCommand({
   meta: {
@@ -17,8 +18,8 @@ const main = defineCommand({
   args: {
     input: {
       type: 'positional',
-      description: 'Input file path',
-      required: true,
+      description: 'Input file path (omit or use "-" to read from stdin)',
+      required: false,
     },
     output: {
       type: 'string',
@@ -62,12 +63,11 @@ const main = defineCommand({
     },
   },
   async run({ args }) {
-    const input = args.input || args._[0]
-    if (!input) {
-      throw new Error('Input file path is required')
-    }
+    const input = args.input
 
-    const inputPath = path.resolve(input)
+    const inputSource: InputSource = !input || input === '-'
+      ? { type: 'stdin' }
+      : { type: 'file', path: path.resolve(input) }
     const outputPath = args.output ? path.resolve(args.output) : undefined
 
     // Parse and validate indent
@@ -82,12 +82,12 @@ const main = defineCommand({
       throw new Error(`Invalid delimiter "${delimiter}". Valid delimiters are: comma (,), tab (\\t), pipe (|)`)
     }
 
-    const mode = detectMode(inputPath, args.encode, args.decode)
+    const mode = detectMode(inputSource, args.encode, args.decode)
 
     try {
       if (mode === 'encode') {
         await encodeToToon({
-          input: inputPath,
+          input: inputSource,
           output: outputPath,
           delimiter: delimiter as Delimiter,
           indent,
@@ -97,7 +97,7 @@ const main = defineCommand({
       }
       else {
         await decodeToJson({
-          input: inputPath,
+          input: inputSource,
           output: outputPath,
           indent,
           strict: args.strict !== false,
@@ -111,106 +111,4 @@ const main = defineCommand({
   },
 })
 
-function detectMode(
-  inputFile: string,
-  encodeFlag?: boolean,
-  decodeFlag?: boolean,
-): 'encode' | 'decode' {
-  // Explicit flags take precedence
-  if (encodeFlag)
-    return 'encode'
-  if (decodeFlag)
-    return 'decode'
-
-  // Auto-detect based on file extension
-  if (inputFile.endsWith('.json'))
-    return 'encode'
-  if (inputFile.endsWith('.toon'))
-    return 'decode'
-
-  // Default to encode
-  return 'encode'
-}
-
-async function encodeToToon(config: {
-  input: string
-  output?: string
-  delimiter: Delimiter
-  indent: number
-  lengthMarker: NonNullable<EncodeOptions['lengthMarker']>
-  printStats: boolean
-}) {
-  const jsonContent = await fsp.readFile(config.input, 'utf-8')
-
-  let data: unknown
-  try {
-    data = JSON.parse(jsonContent)
-  }
-  catch (error) {
-    throw new Error(`Failed to parse JSON: ${error instanceof Error ? error.message : String(error)}`)
-  }
-
-  const encodeOptions: EncodeOptions = {
-    delimiter: config.delimiter,
-    indent: config.indent,
-    lengthMarker: config.lengthMarker,
-  }
-
-  const toonOutput = encode(data, encodeOptions)
-
-  if (config.output) {
-    await fsp.writeFile(config.output, toonOutput, 'utf-8')
-    const relativeInputPath = path.relative(process.cwd(), config.input)
-    const relativeOutputPath = path.relative(process.cwd(), config.output)
-    consola.success(`Encoded \`${relativeInputPath}\` → \`${relativeOutputPath}\``)
-  }
-  else {
-    console.log(toonOutput)
-  }
-
-  if (config.printStats) {
-    const jsonTokens = estimateTokenCount(jsonContent)
-    const toonTokens = estimateTokenCount(toonOutput)
-    const diff = jsonTokens - toonTokens
-    const percent = ((diff / jsonTokens) * 100).toFixed(1)
-
-    console.log()
-    consola.info(`Token estimates: ~${jsonTokens} (JSON) → ~${toonTokens} (TOON)`)
-    consola.success(`Saved ~${diff} tokens (-${percent}%)`)
-  }
-}
-
-async function decodeToJson(config: {
-  input: string
-  output?: string
-  indent: number
-  strict: boolean
-}) {
-  const toonContent = await fsp.readFile(config.input, 'utf-8')
-
-  let data: unknown
-  try {
-    const decodeOptions: DecodeOptions = {
-      indent: config.indent,
-      strict: config.strict,
-    }
-    data = decode(toonContent, decodeOptions)
-  }
-  catch (error) {
-    throw new Error(`Failed to decode TOON: ${error instanceof Error ? error.message : String(error)}`)
-  }
-
-  const jsonOutput = JSON.stringify(data, undefined, config.indent)
-
-  if (config.output) {
-    await fsp.writeFile(config.output, jsonOutput, 'utf-8')
-    const relativeInputPath = path.relative(process.cwd(), config.input)
-    const relativeOutputPath = path.relative(process.cwd(), config.output)
-    consola.success(`Decoded \`${relativeInputPath}\` → \`${relativeOutputPath}\``)
-  }
-  else {
-    console.log(jsonOutput)
-  }
-}
-
 runMain(main)
diff --git a/packages/cli/src/types.ts b/packages/cli/src/types.ts
new file mode 100644
index 0000000..2dd5c9e
--- /dev/null
+++ b/packages/cli/src/types.ts
@@ -0,0 +1,3 @@
+export type InputSource
+  = | { type: 'stdin' }
+    | { type: 'file', path: string }
diff --git a/packages/cli/src/utils.ts b/packages/cli/src/utils.ts
new file mode 100644
index 0000000..9605d90
--- /dev/null
+++ b/packages/cli/src/utils.ts
@@ -0,0 +1,79 @@
+import type { InputSource } from './types'
+import * as fsp from 'node:fs/promises'
+import * as path from 'node:path'
+import process from 'node:process'
+
+export function detectMode(
+  input: InputSource,
+  encodeFlag?: boolean,
+  decodeFlag?: boolean,
+): 'encode' | 'decode' {
+  // Explicit flags take precedence
+  if (encodeFlag)
+    return 'encode'
+  if (decodeFlag)
+    return 'decode'
+
+  // Auto-detect based on file extension
+  if (input.type === 'file') {
+    if (input.path.endsWith('.json'))
+      return 'encode'
+    if (input.path.endsWith('.toon'))
+      return 'decode'
+  }
+
+  // Default to encode
+  return 'encode'
+}
+
+export async function readInput(source: InputSource): Promise<string> {
+  if (source.type === 'stdin')
+    return readFromStdin()
+
+  return fsp.readFile(source.path, 'utf-8')
+}
+
+export function formatInputLabel(source: InputSource): string {
+  if (source.type === 'stdin')
+    return 'stdin'
+
+  const relativePath = path.relative(process.cwd(), source.path)
+  return relativePath || path.basename(source.path)
+}
+
+function readFromStdin(): Promise<string> {
+  const { stdin } = process
+
+  if (stdin.readableEnded)
+    return Promise.resolve('')
+
+  return new Promise((resolve, reject) => {
+    let data = ''
+
+    const onData = (chunk: string) => {
+      data += chunk
+    }
+
+    function cleanup() {
+      stdin.off('data', onData)
+      stdin.off('error', onError)
+      stdin.off('end', onEnd)
+    }
+
+    function onError(error: Error) {
+      cleanup()
+      reject(error)
+    }
+
+    function onEnd() {
+      cleanup()
+      resolve(data)
+    }
+
+    stdin.setEncoding('utf-8')
+    stdin.on('data', onData)
+    stdin.once('error', onError)
+    stdin.once('end', onEnd)
+    stdin.resume()
+  })
+}