Subformer
Free · No signup · Runs in your browser
CSV
JSON

CSV to JSON Converter

Convert a CSV file to JSON in your browser - perfect for piping spreadsheets into scripts, APIs, or LLMs.

Drop one or many - all convert to JSON. Per-row progress, batch convert, ZIP download.

Why convert CSV to JSON?

CSV is the lowest-common-denominator format for tabular data: every spreadsheet exports it, every script ingests it. JSON is the same for nested or self-describing data: every programming language can parse it, every modern API consumes it. Converting CSV to JSON bridges the gap when you need to feed spreadsheet data into a JavaScript script, REST API, or an LLM that thinks in objects.

We parse the CSV with PapaParse, treating the first row as field names and the rest as records. Numeric values are auto-typed; everything else stays as strings. The output is an indented JSON array of objects - ready to paste into a script or pipe into curl. Everything happens locally; no data leaves your browser.

Developer workflows that benefit most: prototyping a REST API with mock data (CSV export from a spreadsheet, JSON into your handler), seeding a database with sample records (CSV from finance/ops team, JSON into a migration script), feeding an LLM a structured dataset for analysis (LLMs handle JSON arrays of objects far better than free-form CSV), and converting business reports into format-machine-readable APIs (Salesforce/HubSpot/Stripe all export CSV, your dashboard probably consumes JSON).

A note on edge cases that often trip up CSV parsers: cells with embedded commas (quoted strings), cells containing literal double-quotes (escaped via doubled quotes), multi-line cells (cells spanning multiple lines inside quotes), Windows line endings (CRLF), and Excel-specific quirks (UTF-8 byte-order mark, "=" prefix to force literal interpretation). PapaParse handles all of these correctly. If you've previously hit "broken at row 47" errors with cheap parsers, PapaParse fixes them.

The auto-typing of numbers is the single most useful default. Without it, a column like "12345" parses as the string "12345" and you can't sort or sum it server-side until you cast. PapaParse detects integers, floats, scientific notation, and booleans-as-true/false. Date strings stay as strings (no auto-parse to a Date object) because date formats are too varied to guess reliably; cast them in your destination code.

Common CSV to JSON use cases

  • API mock data

    Export a spreadsheet of test records as CSV, convert to JSON, serve from a mock endpoint. Faster than typing JSON by hand.

  • Database seeding

    Take a CSV export from another system and convert to JSON for use in a migration or seed script. Most ORMs accept JSON arrays directly.

  • Feeding data to ChatGPT or Claude

    LLMs analyse JSON arrays much more reliably than raw CSV. Convert first, paste in, ask for insights.

  • Dashboard prototyping

    Frontend devs prototyping a dashboard against real data benefit from JSON they can import directly. Faster than wiring up a CSV parser in the prototype.

  • Salesforce / HubSpot exports

    CRM exports usually come as CSV. Convert to JSON for ingestion into custom analytics or sync into a JSON-native database.

  • Migrating between systems

    Going from a legacy CSV-based workflow to a modern JSON-based one starts with this conversion. Useful for one-off migrations and ongoing pipelines.

CSV

About CSV

CSV (Comma-Separated Values) is the simplest tabular format - plain text rows of comma-delimited values. Read by every spreadsheet program, scripting language, and data tool ever made.

JSON

About JSON

JSON (JavaScript Object Notation) is the lingua franca of structured data on the web. Arrays, objects, strings, numbers, booleans. Read by every modern programming language.

How to convert CSV to JSON

  1. 01

    Drop your CSV file

    Drag a CSV onto the converter above, or click the box to pick one from your device.

  2. 02

    JSON is already selected

    We've preselected JSON as the output format. Change it from the dropdown if you want a different target.

  3. 03

    Convert and download

    Click Convert and wait for the progress bar to finish. Download the JSON when it's ready.

CSV to JSON FAQ

See all formats →