What is NumbersChecker?

NumbersChecker is a free online toolbox with 139+ utilities for decoding ciphers, solving puzzles, hashing strings, encoding data, number theory, math, text analysis, and science. No login or installation required.

Is NumbersChecker free to use?

Yes, all 139+ tools on NumbersChecker are completely free. No account, subscription, or installation is required.

What cipher tools are available?

NumbersChecker offers 25 cipher tools including Caesar cipher decoder, Vigenère cipher, ROT13, Atbash, Morse code, Base64, Binary, Hex, A1Z26, Rail Fence, Affine, Polybius Square, Scytale, Columnar Transposition, and more.

Can I use NumbersChecker to solve puzzles?

Yes. NumbersChecker includes 12 puzzle tools including a Wordle solver, Hangman solver, Crossword pattern finder, Kakuro clue calculator, Scrabble word builder, substitution cipher solver, and number sequence solver.

Does NumbersChecker have an API?

Yes. Every tool is available as a free JSON REST API. Send a POST request to https://numberschecker.com/api/{toolId} with your input as JSON. No authentication required.

What hashing tools are available?

NumbersChecker provides MD5, SHA-1, SHA-256, SHA-512, and CRC32 hash generators, plus a hash identifier tool that detects the likely algorithm used for any given hash string.

How do I decode a Caesar cipher?

Go to https://numberschecker.com/tool/caesar, enter your ciphertext, and set the shift amount. The tool also shows a brute-force table of all 26 possible shifts so you can spot the correct decoding at a glance.

What number tools are available?

NumbersChecker has 15 number tools including a base converter (binary, octal, hex, and any base 2–36), Roman numeral converter, prime factorization, GCD and LCM calculator, Fibonacci generator, Euler totient, Chinese Remainder Theorem solver, and number-to-words converter.

NumbersChecker — 139+ Free Online Tools for Ciphers, Math & Puzzles

Ciphers

Caesar Cipher

Shift letters by a fixed number of positions.

ROT13

Rotate letters by 13 positions.

Vigenère Cipher

Polyalphabetic substitution using a keyword.

Atbash Cipher

Reverse the alphabet (A↔Z, B↔Y…).

Morse Code

Encode/decode text to/from Morse code.

Binary Text

Convert text to/from binary (base-2).

Hex Text

Convert text to/from hexadecimal.

Base64

Encode/decode text in Base64.

A1Z26 Cipher

Substitute each letter with its position (A=1…Z=26).

Rail Fence Cipher

Transposition cipher writing in a zigzag pattern.

Playfair Cipher

Encrypt pairs of letters using a 5×5 key square.

Beaufort Cipher

Reciprocal variant of the Vigenère cipher.

Affine Cipher

Linear transformation encryption (ax+b mod 26).

Polybius Square

Map letters to row/column coordinates.

Tap Code

Grid-based knock/tap cipher used by prisoners.

Pigpen Cipher

Geometric substitution cipher (masonic cipher).

Four-Square Cipher

Encrypts pairs using four 5×5 squares.

Running Key Cipher

Vigenère variant using a long text as the key.

Scytale Cipher

Ancient Greek transposition cipher using a rod.

Columnar Transposition

Rearrange columns of text using a keyword.

Gronsfeld Cipher

Vigenère variant using a numeric key.

Porta Cipher

Reciprocal cipher by Giovanni Battista della Porta.

Trithemius Cipher

Progressive shift cipher (keyless Vigenère).

Chappe Telegraph

Visual semaphore telegraphic code.

Navajo Code Talker Numbers

WWII Navajo code talker numeric substitutions.

Encoding

URL Encode/Decode

Percent-encode or decode a URL string.

HTML Entities

Escape/unescape HTML special characters.

Unicode Converter

Convert text to/from Unicode code points.

ASCII Table

Look up ASCII code ↔ character mappings.

Base32

Encode/decode text in Base32.

Base58

Encode/decode text in Base58 (Bitcoin alphabet).

Punycode

Convert internationalized domain names.

Quoted-Printable

MIME quoted-printable encode/decode.

UUencode

Classic Unix uuencode/uudecode.

JWT Decoder

Decode and inspect a JWT token.

Hashing

MD5 Hash

Compute the MD5 hash of a string.

SHA-1 Hash

Compute the SHA-1 hash of a string.

SHA-256 Hash

Compute the SHA-256 hash of a string.

SHA-512 Hash

Compute the SHA-512 hash of a string.

CRC32

Compute a CRC-32 checksum.

Hash Identifier

Identify the likely type of a hash string.

Numbers

Number Base Converter

Convert numbers between any bases 2–36.

Roman Numerals

Convert between Roman numerals and integers.

Prime Number Checker

Check if a number is prime and list factors.

Prime Factorization

Decompose a number into prime factors.

GCD & LCM

Compute GCD and LCM of two numbers.

Fibonacci Sequence

Generate Fibonacci numbers up to N.

Modular Arithmetic

Operations under a given modulus.

Extended Euclidean

Find Bézout coefficients with extended GCD.

Chinese Remainder Theorem

Solve systems of congruences.

Euler's Totient φ(n)

Compute Euler's totient function.

Number to Words

Spell out a number in English words.

Big Number Arithmetic

Add, subtract, multiply large integers.

Continued Fractions

Convert fractions to/from continued fractions.

Collatz Sequence

Generate the Collatz (3n+1) sequence.

Number Bases Table

Show a number in all common bases simultaneously.

Text

Reverse Text

Reverse a string character by character.

Letter Counter

Count letter/character frequencies in text.

Word Count

Count words, lines, and characters.

Anagram Solver

Find all anagrams of a word or phrase.

Text Case Converter

Convert text between cases (UPPER, lower, Title…).

Sort Lines

Sort lines alphabetically or by length.

Remove Duplicate Lines

Remove duplicate lines from text.

Find & Replace

Find and replace text with regex support.

Text Diff

Show differences between two texts.

Lorem Ipsum Generator

Generate Lorem Ipsum placeholder text.

Palindrome Checker

Check if a string is a palindrome.

NATO Phonetic Alphabet

Convert text to NATO phonetic spelling.

Pig Latin

Convert English text to Pig Latin.

Leet Speak (1337)

Translate text to leet speak.

Text Statistics

Readability scores and text statistics.

Regex Tester

Test and debug regular expressions.

Zalgo Text

Add glitchy combining diacritics to text.

Text 180°

Flip text upside down using Unicode.

camelCase ↔ snake_case

Convert between common identifier naming styles.

Word Wrap

Wrap text at a specified column width.

Math

Expression Evaluator

Evaluate mathematical expressions safely.

Matrix Operations

Add, multiply, invert, and find determinants.

Linear Equation Solver

Solve systems of linear equations.

Quadratic Solver

Find roots of a quadratic equation.

Statistics Calculator

Mean, median, mode, std dev, variance.

Permutations & Combinations

Calculate P(n,r) and C(n,r).

Binomial Theorem

Expand (a+b)ⁿ and list binomial coefficients.

Truth Table Generator

Generate a truth table for a boolean expression.

Boolean Simplifier

Simplify Boolean algebra expressions.

Probability Calculator

Calculate basic probabilities and expected values.

Unit Converter

Convert between physical units.

Triangle Solver

Solve any triangle given sides/angles.

Percentage Calculator

Calculate percentages and relative changes.

Number Theory Tools

Perfect, amicable, and abundant number checks.

Set Operations

Union, intersection, and difference of sets.

Puzzles

Substitution Solver

Crack a monoalphabetic substitution cipher via frequency analysis.

Word Search Finder

Find words hidden in a letter grid.

Crossword Pattern

Find words matching a crossword pattern (e.g. _A_T).

Scrabble / Word Builder

Find all valid words from a set of letters.

Number Sequence Solver

Identify and continue numeric sequences.

Rebus Helper

Break down rebus puzzles using phonetics.

Logic Grid Puzzle

Solve logic grid (Einstein) puzzles.

Kakuro Clue Finder

List digit combinations for kakuro clues.

Sudoku Hint

Get hints or solve a 9×9 Sudoku puzzle.

Mastermind Solver

Optimal strategy for the Mastermind code game.

Nonogram / Picross

Validate and partially solve nonogram clues.

Letter Equation Solver

Solve SEND+MORE=MONEY style puzzles.

Date & Time

Date Difference

Calculate the number of days between two dates.

Unix Timestamp

Convert between Unix timestamps and human dates.

Day of the Week

Find the weekday for any date (Zeller algorithm).

Age Calculator

Calculate age in years, months, and days.

Time Zone Converter

Convert a time between world time zones.

Countdown Timer

Countdown to a specific date and time.

ISO Week Number

Find the ISO week number for a date.

Julian Date

Convert between calendar dates and Julian Day Numbers.

Programming

JSON Formatter

Pretty-print or minify JSON data.

JSON ↔ CSV

Convert between JSON arrays and CSV.

CSV Viewer / Editor

Render and edit CSV as an interactive table.

YAML ↔ JSON

Convert between YAML and JSON.

XML Formatter

Validate and pretty-print XML.

Color Converter

Convert colors between HEX, RGB, HSL, CMYK.

HTML Minifier

Strip whitespace and comments from HTML.

Code Diff Checker

Side-by-side diff of two code snippets.

Cron Expression Parser

Explain and validate cron expressions.

IP Address Info

Inspect an IP address: class, binary, subnet.

Subnet Calculator

Calculate subnet ranges from CIDR notation.

UUID Generator

Generate v4 UUIDs.

Password Generator

Generate strong random passwords.

Bitwise Operations

Perform AND, OR, XOR, NOT, bit-shift operations.

Luhn Algorithm

Validate or generate a check digit using the Luhn algorithm (credit cards, IMEI, etc).

Science

Periodic Table Lookup

Look up any chemical element by symbol or name.

Resistor Color Code

Decode or encode resistor color band codes.

BMI Calculator

Calculate Body Mass Index (BMI).

Speed / Distance / Time

Solve any of speed, distance, or time given the other two.

Ohm's Law Calculator

Solve V, I, R, P using Ohm's law.

pH Calculator

Calculate pH from H⁺ concentration and vice versa.

Molecular Weight

Calculate the molecular weight of a chemical formula.

Games

Wordle Solver

Find Wordle candidates from your guesses.

Hangman Solver

Suggest letters and words for hangman.

20 Questions Helper

Binary-search strategy for 20 Questions.

Cryptoquip Solver

Solve substitution cipher quote puzzles.

Countdown Letters

Find the longest word from Countdown letters.

Countdown Numbers

Reach a target using Countdown arithmetic.

139+ free tools one address