Convert CamelCase to snake_case Online
Convert CamelCase to snake_case between CamelCase, snake_case, PascalCase, kebab-case, CONSTANT_CASE and more - batch line-by-line.
Paste one identifier per line and pick a target case. The tool detects word boundaries — lower→upper transitions, separators, and acronym runs — and batch-converts every line to camelCase, snake_case, PascalCase, kebab-case, CONSTANT_CASE, Title Case, or dot.case.
How to Use Convert CamelCase to snake_case Online
- Choose a target case. Seven options: camelCase, snake_case, PascalCase, kebab-case, CONSTANT_CASE, Title Case, and dot.case.
- Paste your identifiers. One per line. Mix input formats freely - the tool tokenizes each line independently. Blank lines are preserved so line numbers stay aligned.
- Press Ctrl/Cmd+Enter or click Convert Case. The input is also debounced at 150ms, so typing produces a live preview without clicking anything.
- Read the output. The right panel mirrors your input row-for-row - each line is its own converted identifier.
- Handle acronyms. "XMLHttpRequest" tokenizes as
xml http requestusing a two-stage regex: first it splits ACRONYM+Word, then lower→upper. Numbers stick to their word ("v2Api" → "v2 api"). - Scan the stats line. Lines processed, lines changed, input/output character counts, and compute time appear below the output.
- Copy or download. Copy puts the entire output on your clipboard. Download saves a .txt report with all stats and a timestamped filename.
Frequently Asked Questions
What is camelCase?
A naming convention where the first letter is lowercase and each subsequent word starts with an uppercase letter, with no spaces or punctuation – e.g. myVariableName. Common in JavaScript, Java, and C#.
What is snake_case?
All lowercase with words separated by underscores – e.g. my_variable_name. Common in Python, Ruby, Rust, and database column names.
What is the difference between camelCase and PascalCase?
PascalCase (a.k.a. UpperCamelCase) capitalises the first letter of every word including the first – e.g. MyVariableName. camelCase keeps the first word lowercase. PascalCase is typically used for class names; camelCase for variables and functions.
When should I use CONSTANT_CASE?
For program-wide constants. All uppercase with underscores – e.g. MAX_RETRIES. Standard in JavaScript, Python, C, C++, and many style guides.
What is kebab-case used for?
URLs, CSS class names, HTML attributes, and CLI flags – anywhere a dash is legal but an underscore or space is awkward. E.g. user-profile.
Can I convert from any case format to another?
Yes. The tokenizer handles camelCase boundaries, acronym runs, digits, and separators (space, underscore, hyphen, dot) all at once. Mix inputs freely on different lines.
How does it tokenize acronyms like “XMLParser”?
It applies two regex passes: first ([A-Z]+)([A-Z][a-z]) splits “XML Parser”, then ([a-zd])([A-Z]) splits normal camelCase boundaries. The result for “XMLParser” is xml parser.
Does this tool work offline?
Yes. After the page loads, every conversion runs locally. You can disconnect from the network and the tool keeps working.
Is my data secure and is this tool free?
Yes on both counts. 100% client-side – the identifiers never leave your browser. Free forever, with no sign-up or usage caps.
How does the tool handle special characters and numbers?
Digits stay attached to the nearest word. Most punctuation other than _ - . space gets dropped during tokenization. So my_var123_name becomes my var123 name, then joins back into the target case.