Add your XLSX file
Drop one or more .xlsx files onto the converter above, or browse for them. They load into browser memory only. Nothing is uploaded, so there is no size-based pricing and no server queue.
XLSX to CBOR
Converting a .xlsx file to .cbor lifts the document's content out of its original format into a portable one. Free, private, and validated: the file never leaves your browser.
Private for supported formats, processed in your browser
Runs on your deviceConvert supported files
Drop XLSX files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting Excel workbook to CBOR
Converting a .xlsx file to .cbor lifts the document's content out of its original format into a portable one. An .xlsx file is a modern Excel workbook, a ZIP archive of SpreadsheetML XML parts describing sheets, shared strings, styles, and formulas. It has been Excel's default save format since 2007 and the de facto interchange format for tabular business data.
A .cbor file holds Concise Binary Object Representation data: a binary format built on the JSON data model but standardized by the IETF, with a tag mechanism that lets it carry dates, big integers, decimals and arbitrary application types without inventing a convention for each one. For this route the practical draw is an actual IETF standard with a stable, versioned specification and tags express types JSON cannot, without breaking decoders that ignore them, balanced against tag semantics are only as portable as the two ends' agreement on them, which is worth knowing before you commit a large batch.
Why convert XLSX to CBOR?
The practical trigger for this conversion is usually a mismatch: with .xlsx, date-as-serial-number storage causes subtle off-by-one and timezone bugs. Switching to .cbor buys you an actual IETF standard with a stable, versioned specification, which is why it is the better fit for WebAuthn and FIDO2 attestation and assertion payloads. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
XLSX vs CBOR at a glance
| Aspect | Excel workbook (.xlsx) | CBOR (.cbor) |
|---|---|---|
| Format type | Text-based: characters and structure, so there is no visual quality loss | Lossless: every pixel or sample is preserved exactly |
| How it stores data | xl/worksheets/sheetN.xml holds rows of typed cells; text cells usually point into xl/sharedStrings.xml to avoid repetition | every item begins with a major type in the top three bits and a length or value in the remaining five, which makes decoders small enough for microcontrollers |
| Strongest at | the standard vehicle for exchanging spreadsheets between organizations | WebAuthn and FIDO2 attestation and assertion payloads |
| Weak spot | date-as-serial-number storage causes subtle off-by-one and timezone bugs | tag semantics are only as portable as the two ends' agreement on them |
| Metadata | docProps/core.xml carries Dublin Core creator and date fields while docProps/app.xml records the generating application and company, both ride inside the ZIP | semantic tags are read and reported; JSON and YAML targets receive their normalized textual form, since neither has a tag mechanism |
Pick CBOR as the output
Select .cbor in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if CBOR is selectable, the route is real and validated.
Convert on your device
Press Convert. A reader for that file's own format opens it in memory on your device and takes out the text and tables; nothing is uploaded.
Verify and download
Each result is checked before the download unlocks: where CBOR has a signature or a structure this converter can read back, the file is re-opened and parsed, and where it has neither, the check is that a non-empty file of the declared type came back. A result that fails is reported as an error instead of being offered for download, and outputs keep the original filename with the .cbor extension.
XLSX to CBOR questions, answered
Will converting XLSX to CBOR lose quality?
There is no visual quality to lose, because xlsx is text-oriented and cbor is lossless-oriented, so the question is structural fidelity. Text, ordering, and basic structure are preserved; complex layout, embedded objects, and styling beyond the target's model are simplified.
Is it private to convert XLSX files here?
Yes. The .xlsx file is processed inside your browser tab and never uploaded. A reader for that file's own format opens it in memory on your device and takes out the text and tables; nothing is uploaded. Close the tab and the file is gone from memory.
Where will the CBOR file work?
Libraries are widely available for C, Rust, Go, Python, Java, JavaScript and .NET, and browsers speak CBOR indirectly through the WebAuthn API. Novus Convert normalizes .cbor locally into a JSON-compatible model and writes JSON, CSV, XLSX, YAML or YML. Tagged values that JSON cannot represent are converted to a documented textual form rather than being silently discarded.
Will the CBOR file be bigger or smaller than my XLSX?
It depends on the content: every item begins with a major type in the top three bits and a length or value in the remaining five, which makes decoders small enough for microcontrollers. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my XLSX file?
In .xlsx, docProps/core.xml carries Dublin Core creator and date fields while docProps/app.xml records the generating application and company, both ride inside the ZIP. Re-encoding through the browser pipeline does not carry embedded metadata into the output, which doubles as a privacy scrub. Check the exported file if you specifically need tags preserved.
Can I convert CBOR back to XLSX?
Yes. The reverse route exists as a separate tool. Bear in mind that round-tripping .xlsx → .cbor → .xlsx is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.