File Content Field Extractor

File Content Field Extractor

Extracts JavaScript regular-expression matches from the UTF-8 text of selected files. Controls are file selection, a field-name label, a regex pattern and an ignore-case checkbox enabled by default. Pattern defaults to a word-bounded four-digit year, two-digit month and two-digit day separated by hyphens. Supply pattern text without /.../ delimiters; there is no flag text box.

The tool always applies global matching, with case-insensitive matching when checked. It returns full matches (match[0]), not captured subgroups, and preserves duplicate matches and file order. Example: text ID42 id7 with pattern id(\d+) and ignore case yields ID42 and id7, not just 42 and 7.

Date example: 2026-09-07 2026-09-08 with the default pattern yields both strings. This recognizes a text shape, not valid calendar dates; dates in DD/MM/YYYY or another local format need a matching pattern. No date conversion, locale-aware numeric parsing or named-field database extraction occurs.

Result rows contain filename, a tab, the chosen field label, then matches joined with a comma followed by a space (, ). A no-match label is shown when no nonempty joined result exists. This is display text, not escaped CSV or structured JSON, and zero-length matches are ambiguous in the displayed join. No dedicated download is supplied for this tool.

Each file supports at most 10,000 matches. Exceeding that limit returns an error instead of a partial result. Refine the pattern or split the source file and retry. Patterns are limited to 256 JavaScript code units, with a 1500 ms worker timeout per file. Zero-length matches advance to avoid an endless loop. The worker is terminated on success, error or timeout.

Requires selected text files; limits are 500 files, 64 MiB per file,128 MiB total input. File.text decodes UTF-8 and may replace invalid sequences. This is not PDF/DOCX parsing, OCR, EXIF extraction or an encoding detector. All processing is browser-local; a complicated expression can time out, and device performance affects completion. On mobile begin with a small text sample and simple pattern, then review results before using larger batches.

Long matches can hit the output budget before the 10000-match limit. Each file budgets the full matched text plus 30 code units per match against 1000000 code units; narrow broad patterns or split the file if this error occurs.