.env File Parser

A parser for .env files that handles the cases real files actually contain: single and double quotes, values spanning several lines such as an RSA private key, a # comment trailing a value, an export prefix left over from a shell script, and keys with nothing after the equals sign. Once parsed, the table shows every key with its value and any trailing comment, and the result exports as JSON for a test fixture, YAML for a Helm chart, export lines for a shell, ENV directives for a Dockerfile, or TOML blocks for a Netlify environment context.

Quoting is the part worth getting right, because the two kinds of quote do different things. Inside double quotes, escape sequences resolve: \n becomes a real newline, \t a tab, \" a literal quote. Inside single quotes nothing resolves and the value is taken exactly as written, which is what you want for a password containing a backslash. Unquoted values are trimmed, and a # after them starts a comment — so a value with a hash character in it needs quotes, or half of it disappears.

${OTHER_VAR} references are deliberately left as written rather than substituted. Whether they expand at all depends entirely on what reads the file: Node's dotenv does it, Docker Compose does it in some positions, and a plain source .env in a shell expands them as shell variables along with anything else that looks like shell syntax. Substituting here would produce a file that is correct for one of those and silently wrong for the others.

Which brings up the thing .env shares with INI: there is no specification. Node, Python, Ruby, Docker Compose and source all disagree on details — whether quotes are stripped, whether export is tolerated, whether multi-line values exist at all. A file that works under one is not guaranteed to work under the next, so test the export you take from here in the environment that will actually read it. The parsing happens entirely in your browser, which is the relevant property for a file that is, by definition, a pile of secrets.