DuckDB Web Shell
shell.duckdb.org
Run SQL over your own CSV or Parquet file without uploading it
No sign-upOn device
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tableconvert.com
Converts a table between CSV, JSON, Markdown, SQL and Excel.
Paste or upload a table and get it back in any of thirty-odd formats — CSV, JSON, Markdown, LaTeX, SQL inserts, YAML, XML, Excel — with an editable grid in the middle so you can fix a stray column before exporting. Every conversion runs in your browser and nothing is uploaded. The free converter takes files up to 10 MB, which covers most exports but not a database dump.
AltFTool does this too
If you would rather not leave the site, CSV to JSON covers the same job here — free, no account, and it runs in your browser.
Open CSV to JSONQuestions
Works the moment the page loads. No account, no email, no trial. Files over 10 MB are refused by the free web converter.
No. TableConvert does the work inside your browser, so the file never leaves your device — you can load the page, disconnect from the network, and it still works. That makes it a reasonable choice for material containing personal data.
Files over 10 MB are refused by the free web converter.
Alternatives
Same category or same task, ordered by how closely they overlap.
shell.duckdb.org
Run SQL over your own CSV or Parquet file without uploading it
datablist.com
Spreadsheet built for cleaning and deduplicating messy list exports
db-fiddle.com
Run a schema and a query against real MySQL, Postgres or SQLite
datasetsearch.research.google.com
Finds published datasets across repositories, governments and journals
mockaroo.com
Generates realistic fake test data in CSV, JSON or SQL
ourworldindata.org
Long-run global data on health, energy and poverty, free to reuse