Question 1

What delimiters does the converter support?

Accepted Answer

The converter supports comma (,), semicolon (;), tab character, pipe (|), and colon (:) as explicit delimiter choices. The 'Auto' setting uses PapaParse's built-in delimiter detection, which counts occurrences of common delimiter characters in the first line and picks the one that appears most frequently. Auto-detection works well for the vast majority of CSV and TSV files exported by spreadsheet applications and databases. If your file uses a more unusual delimiter (such as a caret ^ or tilde ~), you can open the file in a text editor, replace the delimiter with a supported one, and then paste the modified content into the tool.

Question 2

How do nested objects work with the slash notation?

Accepted Answer

When the 'Nested objects (/)' option is enabled, any column header containing a forward slash is interpreted as a nested path. For example, a header named 'address/city' produces { "address": { "city": "..." } } in the output object. Multiple headers sharing the same prefix — such as 'address/city' and 'address/zip' — are merged into the same nested object: { "address": { "city": "...", "zip": "..." } }. This is useful when you receive flat CSV exports from systems that encode hierarchical data as dot-or-slash-notated column names. The feature only handles one level of nesting per slash segment — deeply nested paths like 'a/b/c' produce { "a": { "b": { "c": "..." } } }.

Question 3

Can I convert large CSV files?

Accepted Answer

This tool supports files up to 5 MB, which covers most practical use cases — a 5 MB CSV can contain tens of thousands of rows depending on column count and value lengths. Because all processing happens in your browser's JavaScript runtime, very large files (10 MB or more) may cause noticeable slowness or run out of memory on low-end devices. For files larger than 5 MB, consider splitting the file into chunks using a tool like csvsplit, or use a command-line converter such as csvkit's csvjson command or a Node.js script using the papaparse npm package directly, which supports streaming large files via web workers.

Question 4

Is my data kept private? Does it get sent to a server?

Accepted Answer

Your data never leaves your device. This CSV to JSON converter is entirely browser-based — all parsing and conversion is performed by JavaScript running locally in your browser tab. No CSV content, no converted JSON, and no metadata is transmitted to any server. This makes the tool safe to use with sensitive or confidential data including financial records, employee information, customer lists, health data, and proprietary business data. You can verify this by checking your browser's network activity tab (F12 → Network) and observing that no outbound requests are made when you paste or convert data.

Question 5

What is NDJSON mode and when should I use it?

Accepted Answer

NDJSON stands for Newline-Delimited JSON, also called JSON Lines. In this format, each JSON object is written on its own line with no surrounding array brackets and no commas between records. For example: {"name":"Alice"}
{"name":"Bob"}. This format is the standard import format for MongoDB's mongoimport tool, Elasticsearch's bulk API, and many streaming data pipeline systems like Kafka and Logstash. It is also useful for large datasets because each line can be parsed independently without loading the entire file into memory. Use NDJSON mode when your target system expects one JSON object per line rather than a JSON array.

Question 6

Why do some values stay as strings even with Parse Numbers enabled?

Accepted Answer

The parse-numbers option converts a value to a JSON number only if the entire value passes JavaScript's Number() coercion and the result is not NaN. Values that look like phone numbers (e.g., '0123456789'), zip codes ('01234'), product codes ('007'), or version strings ('1.2.3') may be converted to numbers, losing leading zeros or being rejected entirely. If you need to preserve leading zeros or keep numeric-looking strings as strings, leave parse-numbers disabled. The option is best used for columns that contain genuine numeric data such as prices, quantities, ages, or scores where leading-zero preservation is not needed.

CSV to JSON Converter