What does chmod 755 mean?

The owner can read, write and execute (7); the group and everyone else can read and execute but not write (5 and 5). It is the usual mode for directories and for scripts and programs that others should be able to run.

What is the difference between chmod 644 and 755?

644 has no execute bits: the owner can read and write, others can only read. 755 adds execute for everyone. Use 644 for ordinary files such as HTML, images and config, and 755 for directories and executables, since a directory needs execute to be entered.

What does chmod 777 do and is it safe?

It lets every user on the system read, write and execute the file. That is rarely needed and is a security hole on a shared or internet-facing machine; a web server, for example, should never own writable 777 files. Fix the owner or group instead.

What is the sticky bit (chmod 1777)?

On a directory the sticky bit (octal 1000, shown as t) means files inside can only be deleted or renamed by their owner, the directory owner or root, even though everyone can create files there. /tmp is the classic example and is normally 1777.

Chmod Calculator

File permissions as octal (755) or symbolic (rwxr-xr-x).

About Chmod Calculator

A chmod calculator that converts between permission checkboxes, octal numbers such as 755 or 644 and symbolic notation such as rwxr-xr-x, with the command.

How to use

Tick read, write and execute for the owner, group and others, or type an octal number (644, 4755) or symbolic string (rw-r--r--) directly. The other two views update at once.
Tick Setuid, Setgid or Sticky when a program or directory needs them. They appear as a leading fourth digit and as s or t in the execute position.
Copy the chmod command and read the one-line description to check it says what you meant.

What it does

Each permission class is one octal digit: read is 4, write is 2 and execute is 1, added together. rwx is 7, r-x is 5, r-- is 4.
The optional leading digit holds the special bits: setuid 4, setgid 2, sticky 1, so 4755 is setuid plus 755.
In symbolic form a lowercase s or t means the special bit and execute are both set; uppercase S or T means the special bit is set without execute, which is almost always a mistake.
Pasting a line from ls -l works: a leading file-type character such as d or - is ignored.
Invalid text shows an error and leaves the checkboxes where they were.

Example

Octal      755
Symbolic   rwxr-xr-x
Command    chmod 755 file
Meaning    Owner can read, write and execute; group and others can read and execute.

Privacy

Everything is calculated in the browser. No request is made, and nothing is stored.

Frequently asked questions

What does chmod 755 mean?: The owner can read, write and execute (7); the group and everyone else can read and execute but not write (5 and 5). It is the usual mode for directories and for scripts and programs that others should be able to run.
What is the difference between chmod 644 and 755?: 644 has no execute bits: the owner can read and write, others can only read. 755 adds execute for everyone. Use 644 for ordinary files such as HTML, images and config, and 755 for directories and executables, since a directory needs execute to be entered.
What does chmod 777 do and is it safe?: It lets every user on the system read, write and execute the file. That is rarely needed and is a security hole on a shared or internet-facing machine; a web server, for example, should never own writable 777 files. Fix the owner or group instead.
What is the sticky bit (chmod 1777)?: On a directory the sticky bit (octal 1000, shown as t) means files inside can only be deleted or renamed by their owner, the directory owner or root, even though everyone can create files there. /tmp is the classic example and is normally 1777.

Encode & decode

GUID Generator: One or many UUIDs, version 4 or 7.
ULID Generator: Sortable 26-character IDs with a time prefix.
Password Generator: Random passwords with length and character-set controls.
Hash Generator: MD5, SHA-1, SHA-256, SHA-384, SHA-512 and HMAC for text or a file.
Base64 Encoder / Decoder: Base64, Base32 and Base58 in both directions.
ROT13 / Caesar Cipher: Shift letters by any amount, or ROT13 in one click.
JWT Decoder: Read a token’s header and payload without sending it anywhere.
URL Encoder / Decoder: Percent-encode text for URLs, or decode it back.
HTML Entities: Escape &, < and > for HTML, or unescape them.
Base64 Image Encoder: Image to a Base64 data URL for CSS or HTML, or decode one back.
Random Number Generator: Random integers in a range, one or many, with or without repeats.
Bcrypt Generator: Hash a password with bcrypt, or check one against a hash.
AES Encrypt / Decrypt: Encrypt text with a passphrase using AES-256-GCM, or decrypt it.
Morse Code Translator: Text to dots and dashes, and back.

Data formats

XML ⇄ JSON: Convert between XML and JSON, from text or a file.
YAML ⇄ JSON: Convert between YAML and JSON, from text or a file.
CSV ⇄ JSON: Convert between CSV and JSON, from text or a file.
JSON to TypeScript: Infer TypeScript interfaces from a JSON sample.
JSON to Python Dataclass: Infer Python dataclasses from a JSON sample.
JSON to Pydantic Model: Infer Pydantic models from a JSON sample.
JSON to Go Struct: Infer Go structs with json tags from a JSON sample.
JSON to Rust Struct: Infer Rust structs with serde derives from a JSON sample.
JSON to Kotlin: Infer Kotlin data classes from a JSON sample.
JSON to C# Class: Infer C# classes from a JSON sample.
Base Number Converter: Binary, octal, decimal, hex and any base up to 36.
Text ⇄ Binary / Hex: Text to binary, hex, octal or decimal, and back.
Unix ⇄ UTC: Epoch seconds or milliseconds to a readable date, and back.
Timezone Converter: Convert a time between cities, with DST handled.
Cron Converter: Describe a schedule in words and get the cron expression.
Cron Expression Parser: Explain a cron expression in words and list its next run times.
Days Between Dates: The exact time between two dates, in days, weeks, months and years.
Age Calculator: Exact age in years, months and days, and the next birthday.
Epoch Clock: The current Unix timestamp, live, in seconds and milliseconds.
CIDR / Subnet Calculator: Network, broadcast, mask and host count for an IPv4 CIDR block.
Chmod Calculator: File permissions as octal (755) or symbolic (rwxr-xr-x).

Units & measures

Angle: Degrees, radians, gradians and turns.
Area: Square metres, feet, acres and hectares.
Bits / Bytes: Bits, bytes and every prefix up to petabytes.
Energy: Joules, calories, kilowatt-hours and BTU.
Frequency: Hertz, kilohertz, megahertz and RPM.
Fuel Economy: Miles per gallon, km per litre and litres per 100 km.
Length: Metres, feet, miles, inches and nautical miles.
Power: Watts, kilowatts and horsepower.
Pressure: Pascals, bar, PSI and atmospheres.
Speed: km/h, mph, knots and metres per second.
Temperature: Celsius, Fahrenheit and Kelvin.
Time Unit: Seconds, minutes, hours, days and beyond.
Volume: Litres, gallons, pints and cubic metres.
Weight: Kilograms, pounds, ounces and stone.

Text & code

Lorem Ipsum Generator: Placeholder paragraphs, sentences or words.
Slug Generator: Turn a title into a URL-safe slug.
Text Compare: Diff by line, word or character, unified or side by side.
URL Parser: Break a URL into host, path, query and fragment.
JSON Formatter & Validator: Validate, pretty-print or minify JSON.
JSON Diff: Compare two JSON documents, ignoring key order and formatting.
JSONPath Tester: Query JSON with a JSONPath expression.
SQL Formatter: Format and indent SQL for any dialect.
JavaScript Beautifier: Format minified or messy JavaScript into readable code.
HTML Formatter: Indent and tidy HTML, or strip it down to one line.
XML Formatter: Pretty-print or minify XML, with error positions.
CSS Minifier / Beautifier: Minify CSS, or expand it back to readable rules.
HTML to Markdown: Convert HTML to clean Markdown.
Text Case Converter: camelCase, snake_case, kebab-case, Title Case and more.
Markdown Previewer: Render Markdown as you type.
Whitespace Remover: Strip line breaks, extra spaces or both.
Sort Lines: Sort lines alphabetically, numerically, by length or reversed.
Duplicate Line Remover: Keep each line once.
String Counter: Characters, words, lines and bytes.
Regex Tester: Test a pattern against text with live matches.
Regex Cheatsheet: Regular-expression syntax with examples.

Word play

Palindrome Checker: Does it read the same backwards?
String Reverser / Rotator: Reverse a string or rotate it by n characters.
Roman Numeral Converter: 1984 ⇄ MCMLXXXIV.
NATO Phonetic Alphabet: Spell text out as Alfa, Bravo, Charlie.
Pig Latin Converter: English to Pig Latin and back.
Numeronym Generator: internationalization → i18n.
Leetspeak Translator: Text to l33t and back.
Word Frequency Counter: Which words appear most, and how often.

Images & colour

QR Code Generator: QR codes for text, links, Wi-Fi and contacts.
Barcode Generator: EAN, UPC, Code 128 and more as SVG or PNG.
Barcode / QR Reader: Decode a barcode or QR code from an image.
Color Picker: Pick a colour and copy it in every format.
Image Converter: Convert between PNG, JPEG and WebP, and resize on the way.
Contrast Checker: Contrast ratio of text on a background, against WCAG AA and AAA.
Favicon Generator: Every favicon size from one image.
Image Compressor: Shrink a JPEG, PNG or WebP in the browser.
Gradient Generator: Build a CSS gradient and copy the rule.
Box Shadow Generator: Tune a shadow and copy the CSS.

Reference

ASCII Table: Every ASCII character with its decimal, hex, octal, binary and HTML code.
HTTP Status Codes: Every HTTP status code with what it means and when to use it.
MIME Types: Common MIME types by file extension, searchable.
Port Numbers: Well-known and registered TCP and UDP ports and the services behind them.