I want to convert some NFT metadata JSON files to CSV for opensea.
JSON data like this:
{
"name": "5",
"description": "",
"external_url": "",
"image": "5.png",
"attributes": [
{
"trait_type": "Background",
"value": "DOT-6"
},
{
"trait_type": "Luckbox",
"value": "3"
}
],
"properties": {
"files": [
{
"uri": "5.png",
"type": "image/png"
}
],
"category": "image",
"creators": []
},
"compiler": "NFTexport.io"
}
The “attributes” array, need to be converted to
attributes[Background], attributes[Luckbox] DOT-6, 3
I used Data File Converter, figured out to converting these JSON file to CSV, in a minutes.
1. Open JSON file in DataFileConverter, set JSON options.

2. Set JSON custom columns.

3. Set CSV options.

4.”Next” and “Next”, convert, get the output CSV file.
JSON → CSV reference
Type mapping
| Value kind | in JSON | in CSV |
|---|---|---|
| Int | 1234 (number) | 1234 |
| Decimal | 1234.56 (number) | 1234.56 |
| Float | 1.234e10 (number) | 1.234e+10 |
| Text | "text" (string) | quoted only when it contains a comma or a quote |
| Long text | "multi-line\ntext" (escaped newline inside a string) | must be quoted; line breaks inside force multi-line records |
| Date | "2026-09-18" (string) | 2026-09-18 |
| Datetime | "2026-09-18T14:30:00Z" (string) | 2026-09-18 14:30:00 |
| Binary | "base64:..." (string) | not representable - base64 or hex string |
| Boolean | true / false (boolean) | TRUE / FALSE, or 1 / 0 depending on the writer |
| JSON | nested object or array, kept as structure | the whole JSON value quoted, with internal quotes doubled |
Dialect differences
Both JSON and CSV are file formats, so what differs below is how each one chooses to represent a value.
| Property | in JSON | in CSV |
|---|---|---|
| identifiers | Double quotes; backslash escapes | Double quotes; a literal quote is doubled ("" ) |
| dates | No date type: dates arrive as strings and the reader must p... | Conventional text: 2026-09-18 or 2026-09-18 14:30:00 |
| binary | Not supported natively - base64 inside a string | Not supported |
| separator | Braces and commas | Comma "," |
| encoding | UTF-8 by definition | No declaration - UTF-8 works only with a BOM |
| typing | string, number, boolean, null, object, array - no date type | None - every field is text |
| shape | Nested objects and arrays | Flat table, optional header row |
| ceiling | Whole document is usually parsed into memory | No formal limit; row count bounded by memory |
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