Computes the WCAG 2.1 contrast ratio between a foreground and background color and returns AA/AAA pass/fail (normal text, large text, UI components)
Counts Japanese text by grapheme, breaks it down into zenkaku/hankaku, counts lines, and computes the X (Twitter) post weight (zenkaku=2, hankaku=1, URL=23 flat, limit 280)
Converts PNG/JPEG files (absolute paths) to WebP using the same libwebp WASM encoder (default quality 80) as the browser tool at tools.first-ch.com/webp/. Output defaults to the same directory as each input with a `.webp` extension
Generates schema.org JSON-LD for `organization` / `faqpage` / `service` / `breadcrumb`. Empty fields are omitted automatically. Returns both a `json` object and a ready-to-embed `<script>` snippet
Generates an `llms.txt` file (per the llmstxt.org proposed format) summarizing a site for AI crawlers/agents
Detects the character encoding (UTF-8 / Shift_JIS), BOM and line endings (CRLF / LF / CR) of a file or text and converts it to UTF-8. Useful for diagnosing garbled Japanese CSVs and for normalising line endings. Output is UTF-8 only — encoding *to* Shift_JIS is not supported (no standard API, and a…
Renders [Marp](https://marp.app) Markdown to slides. Emits a self-contained HTML file (theme CSS inlined; opens in a browser and prints one-slide-per-page) and optionally PDF. Ships a bundled Japanese theme `firstch` (firstch-design tokens: paper/ink/vermilion, IBM Plex Sans JP) used as the default…
Generates dummy data for form / CSV-import testing. `mode=records` returns names, kana readings, addresses, postal codes, emails and phone numbers as CSV/TSV/JSON/XLSX with a choice of encoding (UTF-8 / Shift_JIS), BOM and line endings. `format=xlsx` returns a real Excel workbook as base64 (or writ…
Compares two texts (or two files) and returns the added/removed/changed line counts plus a unified diff (`.patch`) — the same logic as the browser tool at tools.first-ch.com/diff/. Lines are matched with patience diff (lines occurring exactly once in both sides become anchors), falling back to Myer…
Explains a cron expression in plain language and returns the upcoming run times — the same logic as the browser tool at tools.first-ch.com/cron/. Parsing follows Vixie cron (`crontab(5)`): ranges, steps, lists, `JAN-DEC` / `SUN-SAT` names and the `@daily`-style shorthands; six fields means the firs…
Encodes text or a file as Base64 and a `data:` URI, and returns ready-to-paste HTML `<img>` / CSS `background-image` snippets — the same logic as the browser tool at tools.first-ch.com/base64/. With `mode="decode"` it turns Base64 or a data URI back into bytes, writing them to `outputPath` when giv…
Breaks a URL's query string into keys and values, edits it (`set` / `remove` / `utm` / `removeTracking` / `sort`) and rebuilds it — the same logic as the browser tool at tools.first-ch.com/url/. Values come back decoded (`%XX` to characters, `+` to a space), and parameters you did not touch are wri…
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