Convert JSON to CBOR
Convert JSON to CBOR right in your browser. Your file is not uploaded to a server.
How to use it
- Drag your .json files onto the area above, or press "Choose files".
- If options are shown, set them as you like. They appear below the file list.
- Press "Convert". The conversion runs on your device, shows its progress and can be cancelled at any time.
- Press "Download" next to a result. With several results, "Download all as ZIP" gets them in one go.
The formats involved
JSON .json
JSON is a text data format for writing values such as objects, arrays, strings and numbers. RFC 8259 explains that numbers within the range of IEEE 754 binary64 can be expected to be read as the same value by different implementations (section 6).
CBOR .cbor
CBOR is a compact binary data format for values similar to those of JSON. RFC 8949 defines indefinite-length items and tags 0 to 3 such as dates and bignums.
What changes in this conversion
- Integers larger than 9,007,199,254,740,991 cannot be stored exactly by JavaScript and may be rounded. When the file contains such numbers, a note is shown with the result.
Limits and things to watch for
- The file size that can be processed depends on your device. The limit for your device is shown in the drop area, and files above it are refused with a message.
- YAML is read with the YAML 1.2 Core rules. Merge keys (<<) are applied, dates are kept as text, and duplicate keys, custom tags and self-referencing aliases are refused.
- TOML, JSON5, INI, plist, MessagePack and CBOR are handled with reading and writing code written for this site. They were tested against the standards and independent tools, but the result can differ in rare cases.
FAQ
Is my file uploaded to a server?
No. Conversion happens only inside this browser, and file names, contents and results are not sent to our servers. Some converters download their conversion program (code) the first time you use them; your files are not sent then either. See the privacy page for details.
Can I convert many files at once?
Yes. Select several files and they are processed one after another; save the results one by one or all at once as a ZIP. How much can be handled at once depends on your device memory and is shown on the page.
Licences and the software used
Programs this converter downloads and uses: js-yaml 5.5.0 (MIT), fast-xml-parser 5.11.2 (MIT) · Open-source licenses
Sources and check date
- RFC 8259 The JavaScript Object Notation (JSON) Data Interchange Format
section 6: numbers, interoperability within IEEE 754 binary64 · 2026-11-10 - RFC 8949 Concise Binary Object Representation (CBOR)
indefinite-length items, tags 0-3 (dates, bignums) · 2026-11-10 - YAML Ain't Markup Language 1.2.2
chapter 10.3 Core Schema · 2026-11-10 - TOML v1.0.0
data types incl. offset / local date-time, inline tables, arrays of tables · 2026-11-10 - JSON5 Standard
comments, single quotes, unquoted keys, trailing commas, Infinity / NaN, hexadecimal numbers · 2026-11-10 - MessagePack specification
formats overview, timestamp extension type (-1) · 2026-11-10 - Extensible Markup Language (XML) 1.0
production [2] Char: allowed characters · 2026-11-10 - Property list DTD (PropertyList-1.0.dtd)
element names: dict, array, key, string, integer, real, true, false, date, data · 2026-11-10 - js-yaml 5.5.0
the YAML library used (MIT) · 2026-11-10 - fast-xml-parser 5.11.2
the XML library used (MIT) · 2026-11-10
Date we opened the original documents ourselves: 2026-11-10. Specifications can change, so read the original again before anything important.