# Proofline > Solve, graph, test and visualise in one notebook — with data, findings and a report. Proofline is a math notebook that runs in your browser. Each cell is a real calculator — symbolic workbench, equation solver with steps, graphing, exact matrices, number theory, statistics tests, graph algorithms, Big-O crossovers, floating point, erasure coding and more — and cells can read the same datasets, so one table flows through several analyses. Batch runs, A/B variants, run history, pinned findings and a printable report turn the results into conclusions you can share. Proofline (Math notebook) is a premium app of usefulweb.site (https://usefulweb.site/): a full program that runs in the browser. Its engine is deterministic and the same functions are exposed as tools, so an agent can compute exactly what the app shows. ## Use it - Landing page: https://proofline.usefulweb.site/ - Workspace (browser app): https://proofline.usefulweb.site/app - open a project with https://proofline.usefulweb.site/app#project= or a template with https://proofline.usefulweb.site/app#template= - Project file format (JSON Schema): https://proofline.usefulweb.site/project.schema.json - Tutorials: https://proofline.usefulweb.site/tutorials - JSON API: POST https://proofline.usefulweb.site/api/v1/tools//calculate (catalog: https://proofline.usefulweb.site/api/v1/tools) - OpenAPI: https://proofline.usefulweb.site/openapi.json - MCP (Streamable HTTP): https://proofline.usefulweb.site/mcp ## Engine tools - [Math Workbench](https://mathworkbench.usefulweb.site/): Simplify, factor, differentiate, integrate, solve, take limits, series and plots in one box. API: POST https://proofline.usefulweb.site/api/v1/tools/math-workbench/calculate · MCP tool `math_workbench` - [Step-by-Step Equation Solver](https://equationsolversteps.usefulweb.site/): Solve linear, quadratic, rational and radical equations or linear systems with every step shown. API: POST https://proofline.usefulweb.site/api/v1/tools/equation-solver-steps/calculate · MCP tool `equation_solver_steps` - [Graphing Calculator](https://graphingcalculator.usefulweb.site/): Plot up to 6 functions or parametric curves with roots, extrema, intersections and SVG/PNG export. API: POST https://proofline.usefulweb.site/api/v1/tools/graphing-calculator/calculate · MCP tool `graphing_calculator` - [Matrix & Linear Algebra Lab](https://matrixlinearalgebralab.usefulweb.site/): Exact-fraction RREF with steps, determinant, inverse, null space, eigenvalues, LU/QR and Ax = b. API: POST https://proofline.usefulweb.site/api/v1/tools/matrix-linear-algebra-lab/calculate · MCP tool `matrix_linear_algebra_lab` - [Number-Theory Lab](https://numbertheorylab.usefulweb.site/): Primality, factorisation, gcd, modular arithmetic, CRT, φ, π(n), Collatz, continued fractions. API: POST https://proofline.usefulweb.site/api/v1/tools/number-theory-lab/calculate · MCP tool `number_theory_lab` - [Probability & Statistics Studio](https://probabilitystatisticsstudio.usefulweb.site/): Distributions, descriptive stats, confidence intervals and t, chi-square and z tests with p-values. API: POST https://proofline.usefulweb.site/api/v1/tools/probability-statistics-studio/calculate · MCP tool `probability_statistics_studio` - [Graph Algorithm Visualizer](https://graphalgorithmvisualizer.usefulweb.site/): BFS, DFS, Dijkstra, Bellman–Ford, A*, MST, topological sort and SCCs on your edge list. API: POST https://proofline.usefulweb.site/api/v1/tools/graph-algorithm-visualizer/calculate · MCP tool `graph_algorithm_visualizer` - [Big-O Crossover Calculator](https://bigocrossovercalculator.usefulweb.site/): When does c₁·n log n beat c₂·n²? Crossover points, log-log chart and run times. API: POST https://proofline.usefulweb.site/api/v1/tools/big-o-crossover-calculator/calculate · MCP tool `big_o_crossover_calculator` - [Erasure-Coding Playground](https://erasurecodingplayground.usefulweb.site/): Reed–Solomon over GF(256): encode data into k + m shards, lose some, rebuild it. API: POST https://proofline.usefulweb.site/api/v1/tools/erasure-coding-playground/calculate · MCP tool `erasure_coding_playground` - [Floating-Point Explorer](https://floatingpointexplorer.usefulweb.site/): See how IEEE-754 half/single/double store a number: bits, exact value, ULP, rounding error. API: POST https://proofline.usefulweb.site/api/v1/tools/floating-point-explorer/calculate · MCP tool `floating_point_explorer` - [Equation Art Studio](https://equationartstudio.usefulweb.site/): Turn math into art: parametric, polar, Lissajous, rose and spirograph curves. API: POST https://proofline.usefulweb.site/api/v1/tools/equation-art-studio/calculate · MCP tool `equation_art_studio` - [Regex Golf Arena](https://regexgolfarena.usefulweb.site/): Match the left list, avoid the right list — in as few characters as possible. API: POST https://proofline.usefulweb.site/api/v1/tools/regex-golf-arena/calculate · MCP tool `regex_golf_arena` - [Keyboard Heatmap Visualizer](https://keyboardheatmapvisualizer.usefulweb.site/): Paste any text: see which keys and fingers do the work on QWERTY, Dvorak, Colemak & co. API: POST https://proofline.usefulweb.site/api/v1/tools/keyboard-heatmap-visualizer/calculate · MCP tool `keyboard_heatmap_visualizer` ## Formats - Import: Proofline notebook (.proofline.json), CSV, TSV or semicolon tables (datasets), Pasted lists and tables, Share link (#project=…), Tables and text from other premium apps (App Bridge) - Export: Proofline notebook (.proofline.json), CSV of datasets, batch runs and result tables, SVG and PNG figures, Markdown report, Printable report (PDF via print), Review reminders (.ics), Share link ## Limits - Cells run on the server: running needs a connection and is rate limited (about 120 calculations per minute). - There are no variables shared between cells; cells share data through datasets and “Continue with” actions. - The instant graph preview understands common functions only; the graphing tool is the reference. - Regex golf cells only test against the puzzle (dry run); leaderboard submissions stay on the tool page. - Batch runs are limited to 200 rows per run and to cells with a single main input. - Share links carry inputs, data and notes, not results; very large notebooks are better shared as files. - On phones the notebook is fully usable, but long matrices and datasets are easier to edit on a larger screen.