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Analyzing an unknown coded message: how to find the right approach
Observe the message before transforming it When a text looks coded, it can be tempting to immediately remove spaces, punctuation or unusual characters. It is usually better to begin by keeping an exact copy of the original message. An extra space, an isolated capital letter, a different accent or even an invisible character may be part of the puzzle. The Code Detector is designed for this initial exploration. It examines the... [read more]
Transpositions, grids and hidden messages: reading text differently
Transposing text without changing its letters In a substitution cipher such as Caesar, characters are replaced while their general order remains unchanged. A transposition does the opposite: the original letters are preserved but rearranged. A transposed text therefore still contains exactly the same characters in the same quantities, even when all recognizable words have disappeared. Rail Fence illustrates this principle... [read more]
Classic codes and ciphers: recognizing the main families
Before decoding: cipher, code or representation? A cipher transforms a message according to a rule and, in some cases, a key. With Caesar, every letter is shifted by the same number of positions. Vigenère instead uses several shifts determined by a keyword. Atbash replaces each letter with the one located at the opposite end of the alphabet. Other systems rely more on a correspondence. With A1Z26, A becomes 1, B becomes 2... [read more]
3 free fitness tools for running pace and interval workouts
Pace Calculator: connect distance, time and running pace The Pace Calculator uses a distance and a time to automatically calculate the average pace in minutes per kilometer and per mile, as well as the corresponding average speed. It can be used after a run to compare performances, but also before a race to turn a target finishing time into an average pace. For example, completing 10 km in 50 minutes corresponds to an average... [read more]
3 free security tools for passwords and hashes
Password Generator: create a truly random secret The Password Generator creates random combinations from 8 to 64 characters using lowercase letters, uppercase letters, numbers and symbols as needed. Each selected character group is represented in the result, and an option can exclude easily confused characters such as 0 and O or 1 and l when the password needs to be copied manually or dictated. The main benefit is avoiding... [read more]
3 free WebDev tools to check and analyze a website
Contrast Checker: quickly check readability 123D6D and #FFFFFF against WCAG AA and AAA thresholds.# The Contrast Checker compares a text color with a background color to calculate their contrast ratio. It can be used to check the main AA and AAA levels defined by WCAG accessibility guidelines. AA is the level generally targeted for accessible websites: normal text requires a contrast ratio of at least 4.5:1, compared with 3:1... [read more]
33 unit converters for everyday and technical measurements
Common conversions The length, weight and mass, volume, area, temperature and speed converters make it easy to switch between metric, imperial and other commonly used units. AppErgo also provides a Historical Length Converter for feet, toises, perches, leagues, cubits and other measurements found in historical documents. Since some of these varied depending on the period or region, custom reference values can also be added. En... [read more]
15 free date tools for calendar calculations
Measure the period between two dates The Days Between Dates tool calculates the exact difference between a start date and an end date in calendar days. Saturdays and Sundays are therefore counted like any other day. It also distinguishes between the difference between two dates and the number of days included in the period: from the 1st to the 3rd of a month, the difference is 2 days, but the period includes the 1st, 2nd and... [read more]
12 free games to play directly in your browser
Strategy for two players or against the computer Tic-Tac-Toe is played on a 3 × 3 grid where X and O take turns until one player forms a line of three symbols. Despite its extremely simple rules, position matters: the center belongs to more possible winning lines than a square on the edge, and the opponent’s threats must constantly be watched. The game can be played by two people on the same device or against the computer... [read more]