Science
Propagate a spacecraft/satellite state vector (r₀, v₀) to time t₀+Δt under two-body gravity via the universal-variable (f-and-g) method, and derive the classical orbital elements
two-body-state-vector-propagatorMath & Numbers
Convert common physical, chemistry, cooking, medical, and information units with the formula and dimensional analysis visible.
unit-converter-with-formulaFinance
Compare supermarket product prices by normalizing them to a common unit (per 100g, per liter, per piece, etc.). Enter products as 'name, price, quantity, unit' per line. Ranks from cheapest to most expensive per unit and shows savings vs the most expensive option.
unit-price-calculatorGames
Test your knowledge with a trivia quiz. Random questions from a built-in English bank across science, history, geography, and general topics. Pick 1 of 4; get your score and accuracy at the end.
trivia-quizText Processing
Flip text upside-down (ɥǝllo) with per-letter rotations, plus optional toggles to keep reading order and protect URLs/emails. Plain Unicode text, no font needed.
upside-down-textText Processing
Add an underline beneath every character via the Unicode combining mark U+0332. Plain text — no HTML needed.
underline-textText Processing
Paste a long text and split it into a numbered X thread that respects the 280-character limit. Splits on word/sentence/paragraph boundaries, auto-adds 1/N numbering, weighs CJK and full-width characters correctly, counts URLs as 23 characters, and shows a live X-style preview card for each tweet with a character meter.
twitter-thread-splitterSecurity
Detect phishing and fraud signals in a URL by deep structural analysis — punycode/IDN homograph attacks (mixed Latin/Cyrillic), embedded credentials (user:pass@host trick), high-risk TLDs, double-encoding and control-character smuggling, subdomain brand deception, and numeric/IP host obfuscation. Static analysis only, no network. Complements the URL Validator (which does basic protocol/IP checks).
url-safety-checkerGenerator
Generate modern unique identifiers: ULID, NanoID, Snowflake and CUID2. Compare formats, decode ULID timestamps and pick the right ID for your system.
uid-generatorFormat Conversion
Convert text to/from Unicode escape sequences (\uXXXX / \u{XXXXXX}) and apply Unicode normalization (NFC/NFD/NFKC/NFKD)
unicode-escape-converterMath & Numbers
Analyze two categorical factors and their interaction with a two-way ANOVA table
two-way-anova-calculatorMath & Numbers
Compare two independent proportions with a pooled two-proportion Z test and confidence interval
two-proportion-z-test-calculator