This tool runs entirely in your browser. Nothing you paste is uploaded.
How you can check →YAML to Properties
Config & InfraConvert application.yml into properties in your browser — with every value SnakeYAML would actually construct resolved, and the round trip checked for real.
The properties file appears here.What the conversion cost
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Counted live by your browser's own Performance Timeline — the same data the DevTools Network panel reads. It cannot see what a browser extension does, and it is not meant to replace checking for yourself: here is how, in thirty seconds .
Converting application.yml to properties
YAML looks like it has more information than a properties file — types, nesting, block scalars — and going backwards means deciding what to do with all of it. This converter runs entirely in your browser, resolves every value the way Spring Boot's own YAML reader (SnakeYAML) actually would, and then does something no other converter in this space does: it converts its own output straight back to YAML and checks that the meaning survived, rather than just showing you text and hoping.
Values are resolved, not copied
A properties file has no types, so every YAML value has to become text — the question is
which text. A quoted value's text is unambiguous. A plain value is not:
no is the boolean false to a YAML 1.1 parser, 0755 is
the number 493, and writing the digits back out as typed would silently assert a value the
real application never held. This tool resolves plain values against the spec you choose —
YAML 1.1 (SnakeYAML, the Spring Boot default) or YAML 1.2 — and only falls back to the exact
typed text where there is genuinely no safe answer: a date, or a number too large to convert
without losing precision.
The round trip is actually checked
After converting, this tool takes the properties file it just produced and converts it
straight back to YAML — reusing the same engine as the
Properties to YAML converter — then compares every
resolved value against the original, by key. A value that only changes spelling on the way
(no becoming false, correctly re-inferred as the same boolean on
the way back) is not reported as a problem. A value that genuinely cannot survive the trip
is named, with the line it came from, so you know exactly what to check before you use the
output.
What this tool refuses to read
Anchors, aliases, merge keys, explicit tags, explicit ? keys and non-string
mapping keys are all named on screen with the line they appear on, rather than converted
approximately or silently ignored. Full YAML is a large specification; implementing part of
it badly would be worse than being honest about the part that is out of scope.
Common uses
- Migrating a Spring Boot service from YAML back to properties for a platform that expects flat keys
- Checking exactly which values a properties file would hold once a YAML parser reads your file
- Auditing a multi-document YAML file before splitting it into Spring Boot's
#---profile sections - Verifying that a hand-edited YAML file still round-trips cleanly through properties
Frequently asked questions
- Why does my no become false?
- Because that is what Spring Boot's YAML reader, SnakeYAML, actually constructs. SnakeYAML is a YAML 1.1 parser, and YAML 1.1 reads a bare no as the boolean false — so writing feature.region=no would assert a value your application never held. false is the honest answer; the receipt explains it wherever it happens.
- Why does 0755 become 493?
- A leading zero means octal under YAML 1.1, so 0755 is the number 493 to a real parser, not the text "0755". Writing the number Spring Boot actually computes, rather than the digits you typed, is the whole point of resolving values instead of copying text.
- What does the round-trip check actually check?
- It converts the properties file this tool just produced straight back to YAML, using the same engine as the Properties to YAML converter, and compares every value against what your file originally meant. A value that only changes spelling — no becoming false and then correctly reading back as false — is not a difference. A value that changes meaning is, and is named on screen with the line it came from.
- What happens to a date?
- It is kept exactly as written. A properties file has no date type, and there is no single correct spelling to convert a YAML date into — so rather than guess, the text survives unchanged and a note says so, rather than the tool inventing an answer.
- Do my comments survive?
- A comment written directly above a key travels with it. A comment written above a whole group of keys (above server: rather than above port:) travels onto that group's first key — the same convention the Properties to YAML converter already uses going the other way. It is a stated placement rule, not a claim about which key the comment was really about, since a properties file has no group of its own to hang it on.
- What YAML does this tool refuse to read?
- Anchors, aliases, merge keys, explicit tags, explicit ? keys and non-string mapping keys — all named on screen with the line they appear on, rather than folded into a generic "invalid YAML" error. The file is valid YAML; this tool is choosing not to represent that particular construct as a flat key.
- Does my file leave my browser?
- No. The parser, the converter and the round-trip check all run in this tab. Nothing is uploaded, logged or stored, and you can confirm it by opening the Network tab before you paste.