Formula-driven physics in 3D: simple and double pendulum with real units, step-by-step or real-time, selectable integrators (Euler, Verlet, RK4) and energy and phase-space plots.

Convert a Unix timestamp (s/ms/µs/ns) or any date to every format (ISO, RFC, syslog, Excel, FILETIME…), with time zones, DST and local-vs-UTC detection.

Decode, verify and sign JWT tokens (header, payload, expiration, algorithms). It is the token inspector; to see the full authentication flow (OAuth2/Bearer) see Auth flows.

Beautify or minify SQL, CSS, HTML and JavaScript code with automatic indentation.

Convert a docker run command with its flags to an equivalent docker-compose.yml file.

Split group expenses and calculate who owes whom with the minimum number of transfers.

A real Postgres database in your browser: write SQL, see tables and relationships as a diagram, and query sample data. No server.

Encodes with parity bits and corrects 1-bit errors; includes SECDED (detects 2), interactive error injection, parity coverage and a noisy-channel simulator.

Create diagrams (flowchart, sequence, ER, Gantt) by writing Mermaid code with real-time preview.

Structurally compare two JSON objects and list added, removed and changed keys.

Generate SHA-256, SHA-384 and SHA-512 hashes directly in the browser using Web Crypto API.

Write SQL against a real Postgres in the browser: schema-aware autocomplete, live validation, warnings and optimization suggestions (indexes, SARGability). No server.

Evaluates advanced mathematical expressions and shows the result as rendered LaTeX.

Resize images, convert between formats (PNG/JPEG/WebP) and get the Base64 encoding.

Chat with LLMs, summarization, translation and sentiment analysis running 100% on your device. No server, no data sent. Powered by Transformers.js.

Merge PDFs, extract pages, add watermarks and view document metadata.

Calculate the real cost of a meeting (one-off and annual if recurring) based on attendees, hourly rate and duration.

Transform data by chaining nodes: filter, derive columns, clean text and select — all in one pass, 100% in your browser. Per-node preview and output to CSV or the Viewer.

Test regular expressions in real time and visualize all matches with their position.

Three views on embeddings (meaning vectors): measure the cosine similarity between texts, project them to a 2D map with PCA and build a mini RAG that retrieves the most relevant chunks. All with models running in the browser.

Apply filters (kernels) to an image and see the resulting feature map: edges (Sobel), blur, sharpen, emboss… the basic operation of a convolutional network (CNN). Edit your own kernel, upload an image and watch the "filter bank" that mimics a CNN's first layer.

Simulate rate limiting algorithms (Token Bucket and Fixed Window) with a visual timeline of accepted and rejected requests.

Calculate the fixed monthly payment (French amortization) and generate the full amortization schedule.

Diagram software/hardware architectures (CI/CD, cloud, AI/MCP agents, data flows) with typed components and simulate load in real time: queues, latency, throughput and bottlenecks. No server.

Calculate the break-even point: how many units you need to sell to cover fixed and variable costs, and the estimated time to reach it.

Train a character-level language model on YOUR text and generate new text in that style. Two modes: by counting (n-gram, instant) or with a neural network trained by gradient descent. Tune the temperature and watch the next-character probability, just like a real LLM. The n-gram mode is a character-level Markov; for chain theory (stationary, PageRank) see Markov chains.

Calculate BMI, ideal weight, basal metabolic rate (Harris-Benedict) and recommended bedtimes.

Extract the text from an image (photo, screenshot, scan) right in your browser, without uploading anything to any server. Upload, drag or paste the image and get the text with each word's box colored by its confidence. Pick the language, fix the uncertain words and copy or download it. Tesseract engine downloaded from the CDN and cached (offline afterwards).

Analyse X.509 certificates in PEM format: subject, issuer, validity dates, SANs, key type and days remaining with a colour indicator.

Compares two texts line by line and shows differences with colour highlighting (added/removed).

Detects and replaces sensitive data (emails, phones, validated cards, IBAN, national IDs, keys and secrets) with Presidio-style operators: replace, redact, mask, reversible token or hash. Ideal to clean logs or prompts before pasting them into an AI. 100% in the browser.

Generate QR codes with size and error correction options. Download as PNG.

Train a decision tree (CART) on 2D data and see how it classifies with yes/no questions: the "staircase" decision regions and the tree drawn node by node. Adjust the depth and watch overfitting; choose Gini or entropy. The interpretable model behind random forests and XGBoost.

Format, minify and validate JSON with error highlighting and key counter.

Evaluate a binary classifier visually and interactively: move the threshold and watch the confusion matrix, precision, recall, F1, the ROC curve (with AUC) and the precision-recall curve (with AP). Adjust the model's quality and class imbalance to understand how some metrics lie and others don't.

Train a real neural network in your browser and watch it learn: pick data (circle, XOR, gaussians, spiral) and an architecture, hit play and see the decision boundary form and the loss drop. Click to have it classify a new point. No server, no downloads.

Ohm's law, series and parallel resistors, and resistor color code decoder.

Analyse and explain in plain language the CORS headers your server sends. Shows what is missing to allow a cross-origin request.

Generate a structured system prompt for AI agents by defining role, objective, constraints and output format.

See the attention mechanism inside transformers (BERT, GPT): type a sentence and watch which words each token "looks at", with the token-to-token attention matrix, multiple heads and the causal mask of generative models. Interactive: click a word to see its attention arcs.

Visual statistics playground for AI: interactive distributions (normal, binomial, Poisson…), softmax and temperature, Bayes and entropy. Tweak parameters and watch the curves, samples and loss live.

Import RDF data (Turtle, JSON-LD, N-Triples, RDF/XML), see it as an interactive graph and query it with SPARQL 1.1 — a whole semantic store in your browser (Oxigraph WASM), no server.

Build URLs with UTM parameters for marketing campaigns or decode an existing URL to extract its parameters. Specialized in campaigns (utm_*); to break down any URL see URL Parser.

Write a list of options and pick one at random with animation. Saves result history.

Transform text between camelCase, snake_case, PascalCase, kebab-case and more.

Markdown editor with real-time preview in split or preview-only mode.

Convert colors between HEX, RGB and HSL with live preview.

Configurable Pomodoro timer with session counter and work, short break and long break phases.

Calculate the statistical significance of an A/B experiment using a two-proportion Z-test. Shows the winner and required sample size.

Generate fake data for testing: names, emails, phones, IPs, UUIDs, dates, IBAN and more.

Convert between JSON, YAML, Properties, ENV and CSV with automatic input format detection.

Scoreboard for matches with multiple players, customizable scoring and integrated timer.

Calculate the contrast ratio between two colours and verify WCAG 2.1 AA and AAA compliance for normal and large text.

See how models learn: a ball rolls down a loss surface with SGD, Momentum, RMSProp or Adam. Change the learning rate and momentum and watch the animated trajectory; try local minima and Rosenbrock.

Break a signal into its frequency spectrum (FFT) and rebuild it from a few frequencies; apply convolution kernels (blur, edge) sliding over the signal. The basis of audio, vision and CNN filters.

Visual digital circuit simulator with AND, OR, NOT, NAND, NOR, XOR and XNOR gates. Connect nodes, toggle inputs and watch signal propagation in real time.

Visualize and edit Basic, Bearer/JWT and OAuth2 (Authorization Code and PKCE) as step-by-step sequence diagrams. Here you see the protocol/flow; the JWT is one step — to inspect the token in detail see the JWT inspector.

Break a URL into its parts (protocol, host, path, query params) and build new ones.

Escape and unescape text to embed it in SOURCE CODE: JavaScript, JSON, SQL, Regex, HTML, URL and CSS. To encode for transport (Base64/URL/HTML) see Encoder/Decoder.

Generate secure passwords with configurable options and cryptographically secure UUIDs v4.

Visualize CSV data as line, bar, area, pie, or scatter charts. Export as PNG.

Check which package versions satisfy a semantic version range (^, ~, >=, -) and view the syntax cheatsheet.

Simulates a simplified MIPS ISA in the browser. Editor with active-line highlighting, registers, memory, stack and console. Step-by-step or automatic execution with adjustable speed.

Visual Visio-style diagram editor: drag shapes, connect and edit them. Import and export Mermaid.

chmod (octal/symbolic permissions with special bits), chown and a users & groups command builder (useradd, usermod, groupadd) with warnings and a per-flag explanation.

Build a quantum circuit with qubits and gates (H, X, Y, Z, CNOT, Toffoli...) and watch superposition, entanglement, the Bloch spheres and measurement live. Bell, GHZ and Grover demos.

Look up full information for any character: codepoint, UTF-8/16, HTML entity and ASCII table.

Pack a whole project (or a snippet) into a single text ready to paste into an AI: removes comments, minimizes and shields secrets, IP and sensitive data. 100% in the browser — your code is never uploaded to any server.

Open and explore CSV, logs or JSONL of tens or hundreds of GB without loading them into memory: virtual scroll, go to line, "tail" and streaming text/regex search. 100% local.

Drag points and see the least-squares fit live. Raise the polynomial degree to watch overfitting and use regularization (ridge = MAP with a Gaussian prior) to control it. MSE = maximum likelihood with Gaussian noise.

Visualize how LLMs split text into tokens, compare costs across models (GPT-4, Claude, Gemini, Llama) and estimate how much of the context window your text consumes.

Paste one or more skaffold.yaml and see the dependency graph (requires). It validates cross-references: a requires pointing to a misspelled config name shows in red. Rename a config and its requires update. No server.

Agent-based market simulation: firms competing (Cournot), monopolies, mergers, limited resources and government policy, with a timeline. Understand why prices move (e.g. why RAM gets pricier as HBM is prioritised for AI). No server.

Statistics calculator (descriptives, charts), interactive distributions and probability simulators to understand data and uncertainty.

Preview LaTeX mathematical formulas in real time with example snippets.

Convert between availability percentage (99.9%, 99.99%…) and maximum downtime per hour, day, week, month and year.

Calculate network, broadcast, host range, mask and usable hosts from CIDR notation.

Calculate how inflation erodes money's value year by year with a global or per-year custom rate.

Generate and validate cron expressions with a visual builder, text humanisation and next execution times.

Simulate the monthly cost of using different AI models based on your request volume and prompt size.

Calculate capital growth with monthly contributions and annual compound interest.

Project high-dimensional data (or embeddings) to 2D with PCA, t-SNE and UMAP, and watch them organize live. Compare the linear method (PCA) with the non-linear ones, try the swiss roll and tune perplexity/neighbors. It teaches the algorithms with generic data; to project real sentences see the Semantic map.

Walk a Markov chain and watch the visit distribution converge to the stationary one; or train a Markov text generator. The basis of MDP, PageRank, MCMC and classic text generation. It teaches chain theory; to train a language model with your text see Mini-LLM.

Encode or decode text for TRANSPORT: URL, Base64 and HTML entities. To escape text inside source code (JS, JSON, SQL, Regex, CSS…) see String escaping.

Converts between bases (2–64) and adds a programmer's calculator (arithmetic and bitwise, two's complement), bit inspector, IEEE 754 and codes (ASCII, Gray, endianness).

Converts between bits, bytes and their multiples according to SI (kilo/mega) and IEC (kibi/mebi) standards.

Generate the Nginx config or Apache .htaccess to correctly serve a Single Page Application with client-side routing.

Visually understand p-values, the rejection region and the α level; run t-test, χ², ANOVA and analyze power (type I/II error). To validate whether a model improvement is real or just noise.

Independent dice tables with numeric and symbolic dice. Roll all at once or per table.

Stopwatch with laps and history. Hundredths of a second precision and copy results button.

Generate real, elven, Norse, sci-fi or Japanese-inspired names. Copy all with one click.

See the diffusion process behind generative AIs like Stable Diffusion: a structured point cloud dissolves into Gaussian noise step by step, and the reverse process rebuilds it.

Discover groups in unlabeled data (unsupervised learning) and compare k-means with DBSCAN live. Watch the centroids converge step by step, try "Moons" and "Rings" to see where k-means fails and DBSCAN succeeds, and tune k, eps and minPts.

Calculate how many months of cash your company has left with optimistic, current and pessimistic scenarios.

Classify your team as Elite / High / Medium / Low based on the four DORA metrics: deployment frequency, lead time, MTTR and change failure rate.

Calculate days between dates, exact age in years/months/days, day of the week and date operations.