Rules reference

intern ships 36 rules across four categories. Every rule has a stable id you can pass to --rules or --disable, or configure under [rules.<RULE_ID>] in .intern.toml.

Rules are either on (run by default) or off (must be opted in via enabled = true in [rules.<RULE_ID>] or named in --rules). The status is shown in the tables below.

Alignment

Geometric checks. All compare positions within a configurable pixel threshold.

Margin consistency (cross-slide)

Groups are treated as single units - only the group’s bounding box is considered, not its individual children.

Rule	Status	What it catches	Default threshold
`LEFT_MARGIN`	on	Slide’s leftmost unit is off the typical left margin	10 px
`RIGHT_MARGIN`	on	Slide’s rightmost unit right edge is off the typical right margin	10 px
`BOTTOM_MARGIN`	on	Content extends deeper than the typical bottom margin (overflow only)	10 px
`TITLE_MARGIN`	on	Gap between title and nearest content unit differs from the typical gap	5 px

Proximity alignment (per-slide)

Rule	Status	What it catches	Default threshold
`CLOSE_X`	on	Two units on the same slide have X positions within threshold - likely misaligned	5 px
`CLOSE_Y`	on	Two units on the same slide have Y positions within threshold - likely misaligned	5 px

Other alignment

Rule	Status	What it catches
`TITLE_Y`	on	Title top edge inconsistent across slides
`TITLE_X_WIDTH`	on	Title left edge or width inconsistent across slides
`TEXT_ELEMENT_OVERLAP`	on	Two text-bearing elements on the same slide have overlapping rects
`ELEMENT_OVERFLOW`	on	Element extends outside the slide bounds

Typography

Rule	Status	What it catches	Limit
`TITLE_FONT_SIZE`	on	Title font size differs from the majority	-
`FONT_SIZE_VARIETY`	on	Too many distinct body font sizes across the deck	3 sizes
`BODY_FONT_FAMILY`	on	Body font family differs from the majority across slides	-
`BODY_TEXT_COLOR`	off	Body text color differs from the majority across slides	-
`FONT_VARIETY`	on	Too many distinct font families across the deck	4 families
`COLOR_VARIETY`	on	Too many distinct text colors across the deck	6 colors

BODY_TEXT_COLOR is off by default: color varies intentionally in most decks (branded slides, dark backgrounds, highlighted callouts).

Text quality

Rule	Status	What it catches	Limit
`DOUBLE_SPACE`	on	Paragraph contains two or more consecutive spaces	-
`LEADING_SPACE`	on	Paragraph starts with whitespace	-
`ALL_CAPS`	off	Paragraph text is ALL CAPS	-
`REPEATED_WORD`	on	Two consecutive identical words (“the the”)	-
`BULLET_CAPITALIZATION`	on	Bullets have inconsistent first-letter capitalization	-
`BULLET_PUNCTUATION`	on	Bullet ending punctuation is inconsistent across the deck	-
`BULLET_LENGTH`	on	Bullet is too long	20 words

ALL_CAPS is off by default: common in corporate decks for KPI labels, callout boxes, and section stamps.

Structure

Rule	Status	What it catches	Limit
`TITLE_PRESENT`	off	Slide has no title element	-
`TITLE_LENGTH`	on	Title is too long	10 words
`TITLE_TRAILING_PUNCT`	on	Title ends with `.` `,` `:` or `;`	-
`DUPLICATE_TITLE`	on	Title text is duplicated on another slide	-
`EMPTY_TEXTBOX`	on	Text box has no text content	-
`SLIDE_COUNT`	off	Deck has too many slides	20 slides

TITLE_PRESENT is off by default: section dividers and full-bleed image slides legitimately have no title element.

SLIDE_COUNT is off by default: the 20-slide limit is too deck-specific to be a useful default.

intern fix repairs the rules with an unambiguous correction - the alignment rules (snap to the peer median), the font-size rules, and DOUBLE_SPACE / LEADING_SPACE (normalise whitespace). The remaining text-quality and structural rules report the problem but leave the wording to you.

Threshold

Geometric comparisons use EMU (English Metric Units). The default threshold for most alignment rules is 2 px. The margin and proximity rules have their own defaults (10 px for LEFT_MARGIN, RIGHT_MARGIN, BOTTOM_MARGIN; 5 px for TITLE_MARGIN, CLOSE_X, CLOSE_Y). The global --threshold flag affects only rules that use the 2 px default; per-rule overrides always win:

intern check deck.pptx --threshold 5

# in .intern.toml - overrides the per-rule default for that rule only
[rules.LEFT_MARGIN]
threshold = 15

The word- and count-based limits (TITLE_LENGTH, BULLET_LENGTH, FONT_VARIETY, COLOR_VARIETY, SLIDE_COUNT) are tuned in each rule’s [rules.<RULE_ID>] table - see Configuration.

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