Format Detection

axm-smelt auto-detects the input format before applying strategies.

Supported Formats

Format	`Format` enum value	Detection
JSON	`Format.JSON`	Starts with `{` or `[` after stripping whitespace
YAML	`Format.YAML`	Contains `---` separator or YAML-like `key: value` patterns
XML	`Format.XML`	Starts with `<` (excludes known HTML root tags)
TOML	`Format.TOML`	Parses cleanly with `tomllib.loads`
CSV	`Format.CSV`	`csv.Sniffer` finds a delimiter and ≥2 rows share a consistent column count
Markdown	`Format.MARKDOWN`	≥2 distinct indicators: multi-level headings, pipe tables, fenced code blocks, inline links
Plain text	`Format.TEXT`	Fallback

Detection heuristics

Detection is heuristic and fast — no full parsing is required. The detector inspects:

The first non-whitespace character (for JSON, XML)
Line patterns (for YAML, TOML, CSV, Markdown)
Falls back to TEXT when no pattern matches

For JSON, the detector only checks the first character ({ or [). If json.loads() subsequently fails inside a strategy, the strategy returns the input unchanged.

Strategy behavior by format

Each strategy targets specific formats and returns the input unchanged on any other format (a no-op that the keep-if-reduced guard treats as skipped):

Strategy	Category	Works on	Behavior on other formats
`minify`	whitespace	JSON, YAML, XML	Returns input unchanged
`drop_nulls`	structural	JSON	Returns input unchanged
`flatten`	structural	JSON	Returns input unchanged
`tabular`	structural	JSON	Returns input unchanged
`dedup_values_with_refs`	structural	JSON	Returns input unchanged
`round_numbers`	cosmetic	JSON	Returns input unchanged
`strip_quotes`	cosmetic	JSON	Returns input unchanged
`collapse_whitespace`	whitespace	prose / Markdown (skips structured formats)	Returns input unchanged
`compact_tables`	whitespace	Markdown	Returns input unchanged
`strip_html_comments`	cosmetic	prose / Markdown	Returns input unchanged

minify handles YAML and XML in addition to JSON; the three prose strategies (collapse_whitespace, compact_tables, strip_html_comments) target Markdown / plain text. Running a JSON-only strategy on YAML, XML, or plain text is safe — the input is returned unmodified.

strip_quotes is JSON-only by construction: its "word": pattern would also match quoted words in prose, so it is guarded to Format.JSON and never mutates non-JSON text.

Accessing detected format

Python

from axm_smelt import smelt
from axm_smelt.core.models import Format

report = smelt(data)
print(report.format)          # Format.JSON
print(report.format.value)    # "json"

if report.format == Format.JSON:
    print("JSON detected")