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Data & charts studio

Chartroom

Import data, chart it, run analyses and publish a report — one workspace, free.

Launch Chartroom → Tutorials

Chartroom is a data workspace that runs in your browser. Import CSV, TSV or Excel files, draw live charts, then send the same dataset through site tools for time-series trends and anomalies, maps, statistics and A/B tests, freshness checks, unit conversion and address checks. Public datasets (electricity, public spending, package downloads, web archive, satellite images) flow in as tables, snapshots compare data over time, and everything ends in one report with clear findings that you can print, embed or share.

Free · runs in your browser · no sign-up · Version 1.1.0

Chartroom workspace with the project list on the left, chart settings next to it and a stacked bar chart of revenue by month and region with its findings

Screenshots

Features

  • Data workspace

    Paste a table or open CSV, TSV or Excel (.xlsx) files: they are read on your device, columns are typed (numbers, dates, text) and profiled with missing values, ranges and top values.

  • Live charts

    Line, area, bar, stacked, horizontal bar, scatter, pie, donut and histogram with grouping, aggregation, top N and a target line — the preview redraws as you change a setting.

  • One dataset, many tools

    Add workflow steps that run site tools on the same data: chart studio, time-series explorer, geo visualizer, statistics studio, DataFresh, UnitProof and LocaleKit.

  • Trends and anomalies

    The Time Series Explorer finds the trend, weekday or monthly seasonality and unusual values; Chartroom turns them into plain findings.

  • Maps and diagrams

    Points, proportional circles, hexbins and choropleths from coordinates or country codes, plus flowcharts — including a diagram of how data flows through your project.

  • Statistics and A/B tests

    Descriptive statistics, confidence intervals and Welch t-tests between two groups or two columns, with p-value, effect size and a sentence that says what it means.

  • Public datasets

    Fetch electricity generation and prices, public spending awards, npm/PyPI/crates downloads, Wayback Machine page changes and satellite before/after images straight into the project.

  • Reusable preparation recipes

    Trim spaces, change case, remove duplicates, split a column or left join another dataset in an ordered recipe with a live preview. The result is a new dataset that remembers its recipe: re-run it when the source changes, or download the recipe and load it in another project.

  • Data checks and unit conversion

    DataFresh tells you whether an export is stale and which fields appeared or vanished; LocaleKit checks postal codes and phone numbers row by row; UnitProof verifies a column conversion (miles to km, °F to °C …) before Chartroom applies it.

  • Comparisons over time

    Snapshots keep earlier versions of a dataset: see added, removed and changed rows and how column totals moved. Re-runs show how each finding changed since the last run.

  • Run all, in order

    One click refreshes public data and re-runs every step with progress, retry and automatic pauses when the server asks for them; outdated results are marked.

  • Report and dashboard

    Every chart, map and finding in one report with your introduction and conclusion — print it to PDF, export standalone HTML embeds or download the charts as SVG and PNG.

  • Refresh reminders

    Plan when each dataset needs new data and export the reminders to your calendar as an .ics file with repeating events.

  • Local-first projects

    Autosave and recent projects in your browser, project files, undo/redo, share links, Google Drive saving when signed in — no account needed.

  • Hand data between apps

    Send charts (SVG/PNG) and tables to other usefulweb apps and open tables or JSON from them, without uploading anything.

  • API and MCP

    Every tool Chartroom uses is available as a JSON API and MCP tool, and agents can build projects from the documented JSON schema.

Templates

Start from a ready-made project and change it to fit.

Built-in tools

Chartroom uses these tools. Each one also has its own page and works on its own, in the browser, through the JSON API and through MCP.

For AI agents

Chartroom runs on a deterministic engine. The same functions are available as tools with a JSON API and MCP, so scripts and AI agents get exactly the results the app shows.

  • CSV/Excel Chart Studio – Turn CSV, TSV or Excel data into line, bar, pie, scatter or histogram charts with SVG/PNG export.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/csv-excel-chart-studio/calculate · MCP csv_excel_chart_studio
  • Time-Series Explorer – Resample, smooth and decompose date/value data: trend, R², seasonality, YoY change and anomalies.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/time-series-explorer/calculate · MCP time_series_explorer
  • Geo Data Visualizer – Map CSV coordinates or GeoJSON as points, proportional circles, hex-bin heatmaps or choropleths.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/geo-data-visualizer/calculate · MCP geo_data_visualizer
  • Diagram & Flowchart Maker – Write flowcharts, sequence diagrams and mind maps as text and get a laid-out SVG/PNG diagram.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/diagram-flowchart-maker/calculate · MCP diagram_flowchart_maker
  • Embeddable Chart Builder – Make a self-contained chart to embed anywhere: inline SVG, standalone HTML, accessible snippet.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/embeddable-chart-builder/calculate · MCP embeddable_chart_builder
  • Probability & Statistics Studio – Distributions, descriptive stats, confidence intervals and t, chi-square and z tests with p-values.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/probability-statistics-studio/calculate · MCP probability_statistics_studio
  • DataFresh – Is this dataset or API still fresh? Newest record, update cadence check and schema drift.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/datafresh/calculate · MCP datafresh
  • UnitProof Unit Calculator – Unit maths you can audit: dimension check, exact factors and a full derivation tree.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/unitproof/calculate · MCP unitproof
  • LocaleKit Country Format Rules – Address form fields, postal-code regex, calling code and date formats for any country.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/localekit/calculate · MCP localekit
  • Energy Grid Explorer – Generation mix, load, renewable share, cross-border flows and power prices for European grids.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/energy-grid-explorer/calculate · MCP energy_grid_explorer
  • Public Spending Explorer – Search government contracts and grants: who pays whom, totals per agency and vendor.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/public-spending-explorer/calculate · MCP public_spending_explorer
  • Software Adoption Explorer – Open-source usage signals: weekly downloads, growth and version adoption for npm, PyPI, crates.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/software-adoption-explorer/calculate · MCP software_adoption_explorer
  • Internet Archive Change Explorer – See how a web page changed in the Wayback Machine: capture timeline plus the changes that matter.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/internet-archive-change-explorer/calculate · MCP internet_archive_change_explorer
  • Satellite Change Explorer – Compare NASA satellite images of any place on two dates: true colour, NDVI, night lights.
    Tool page · POST https://chartroom.usefulweb.site/api/v1/tools/satellite-change-explorer/calculate · MCP satellite_change_explorer

Build a project through the API, then open it in the app with a link to https://chartroom.usefulweb.site/app#project=<base64url JSON>.

Import & export

Import

  • CSV, TSV, TXT (comma, semicolon, tab or pipe)
  • Excel workbook (.xlsx, read on your device)
  • JSON (array of objects or headers + rows)
  • Chartroom project (.chartroom.json)
  • Project link (#project=…)
  • Tables and JSON from other usefulweb apps

Export

  • Chartroom project (.chartroom.json)
  • CSV per dataset and per chart
  • SVG and PNG charts
  • Standalone HTML chart and embed snippet
  • Printable report (PDF via print)
  • Calendar reminders (.ics)
  • Snapshot comparison (CSV)

Keyboard shortcuts

Keyboard shortcuts in Chartroom
KeysAction
Ctrl + Z / Ctrl + YUndo / redo
Ctrl + SSave project file
Ctrl + OOpen project or data file
Ctrl + EnterRun the selected step
Ctrl + Shift + EnterRun all steps
Ctrl + PPrint the report
NAdd a step
IImport data
ROpen the report
Alt + ↑ / Alt + ↓Previous / next item in the project
DeleteDelete the selected item (in the project list)
?Keyboard shortcuts

Frequently asked questions

Is Chartroom free, and where is my data?

Yes. Projects are saved in your browser (IndexedDB) and as files you download. Local charts, the data view, snapshots and comparisons run on your device. When you run a tool step, the dataset (or the settings for public data) is sent to usefulweb.site’s API for that one calculation; results come back into your project.

Which file formats can I import?

CSV, TSV and other delimited text (comma, semicolon, tab, pipe; decimal commas are detected per column), Excel .xlsx workbooks (read locally, cached formula values are used) and JSON arrays of objects. Old .xls files need to be saved as .xlsx or CSV first.

What is the difference between a local chart and a chart studio step?

A local chart is drawn instantly in your browser while you edit. The CSV/Excel Chart Studio step renders the same kind of chart on the server with its own column detection, and returns SVG and PNG files plus the data table — useful as a second opinion and for exports.

Why does a step say it has to wait?

Heavy tools (charts, maps, time series, diagrams) are limited to a few calls per minute per visitor and public-data tools to about fifteen. Chartroom queues the steps, waits as long as the server asks and then continues on its own; you can keep editing meanwhile.

How do comparisons over time work?

Whenever a public-data step refreshes a dataset or you replace its data, Chartroom keeps a snapshot of the old version. Compare shows added, removed and changed rows and how column totals moved. Every step also remembers its last runs, so the report can say how a metric changed since the previous run.

Can I share a project?

Yes: save the .chartroom.json file, use Google Drive when you are signed in, or copy a share link. Share links contain the datasets and steps but not the tool results (they would make the link too long); the recipient presses Run all.

What does Prepare data… do to my original dataset?

Nothing. The recipe runs on a copy: operations apply in order (trim, lowercase/uppercase, remove duplicate rows, split at the first delimiter, left join on exact key values) and the result is saved as a new dataset. That dataset keeps the recipe, so Re-run recipe applies it again to the current source data, and Edit recipe… changes it; both are undoable. Joins keep rows without a match and repeat a row when several rows match.

Can an AI agent build a Chartroom project?

Yes. The project format is published as a JSON schema at /project.schema.json; an agent can create datasets and steps and open them with /app#project=<base64url JSON>. All fourteen tools are available through the app’s JSON API and MCP server.

Limitations

What Chartroom does not do (yet):

  • Datasets are limited to 50,000 rows and 200 columns per table (5 MB of CSV text in a project); heavy analyses take at most 2 MB per tool call.
  • Tool steps need a connection to usefulweb.site; offline you can still edit data, draw local charts, compare snapshots and read stored results.
  • Excel formulas are not recalculated: the values cached in the file are used. Charts and pivot tables inside workbooks are not imported.
  • Satellite images open from NASA’s servers in a new tab; the workspace shows their metadata and dates, not the pictures themselves.
  • Row-by-row checks (postal codes, phone numbers) run up to 500 rows per batch and respect the API rate limit, so large batches take a few minutes.
  • There is no live database connection or scheduled background refresh: refreshes run when you press Run all, and reminders go to your own calendar.
  • Tool results are shown in English when the tool itself does not translate them yet.
  • Preparation recipes offer six operations (trim, lowercase, uppercase, remove duplicates, split at a delimiter, exact-key left join) — no formulas, type conversions or fuzzy matching — and re-run only when you press Re-run recipe.

Tutorials

Learn Chartroom step by step.

  1. Your first chart and report in 5 minutesPaste a table, pick a chart type, add an analysis step and print a report — the whole Chartroom workflow with your own data, no account needed.Beginner 5 min
  2. Import CSV and Excel files the right wayHow Chartroom reads delimiters, decimal commas, dates and Excel workbooks, how to replace or append data, and how snapshots protect the old version.Beginner 6 min
  3. Trends, seasonality and anomalies in time seriesSend a date-based dataset through the Time Series Explorer, read the trend, weekday or monthly pattern and anomalies, and track how they change between runs.Intermediate 7 min
  4. Public datasets, snapshots and comparisons over timeFetch electricity, spending, package-download or web-archive data into a dataset, refresh it with Run all and compare every refresh with the previous version.Intermediate 8 min
  5. Maps, embeddable charts and diagramsTurn coordinates or country codes into world maps, publish a self-contained chart on your website, and draw a flowchart of how data moves through your project.Intermediate 7 min
  6. Data checks, batch runs and automation with the APICheck freshness and schema drift, convert a column with a verified factor, validate postal codes row by row, and build Chartroom projects from scripts or AI agents.Advanced 9 min
  7. Clean and join data with reusable recipesUse Prepare data… to trim, split, deduplicate and join a dataset in an ordered recipe, save the result as a new dataset and re-run the recipe when the source changes.Intermediate 7 min

Ready to try it?

Launch Chartroom →

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