Cursor rules vs GEMINI.md vs Cline rules

Every comparison page on the web is a capability table someone wrote from the vendor docs in an afternoon. None of them can tell you how many real repositories ship each file, how long the median one runs, or how often two of them turn up in the same project. Those answers need a corpus, and RuleStack counts one every night.

Measured — counted from real repositories, nightlyAsserted — read from the vendor docs, dated

CompareAGENTS.md CLAUDE.md Cursor rules Copilot instructions Cline rules GEMINI.md .cursorrules Windsurf rulestwo to five

Format	Cursor rules 2026-08-02	GEMINI.md 2026-08-01	Cline rules 2026-08-01
Asserted — what the docs say it can express
File	.cursor/rules/*.mdc	GEMINI.md	.clinerules
Status	vendor	vendor	vendor
Cross-tool	No	No	No
Tools that read it	Cursor	Gemini CLI Gemini Code Assist	Cline Roo Code
Frontmatter	Yes	No	No
Glob targeting	Yes	No	No
Imports other files	Yes	Yes	No
Nested / per-directory	Yes	Yes	No
Multiple files	Yes	Yes	Yes
User-level scope	No	Yes	Yes
When it applies	Four modes set in frontmatter: Always Apply (every chat session), Apply Intelligently (the agent picks it by description), Apply to Specific Files (globs match the edited file), and Apply Manually (@-mentioned). Rules must carry the .mdc extension — a plain .md file in .cursor/rules is ignored.	Hierarchical memory: a global ~/.gemini/GEMINI.md, then the project file, then nested files, concatenated from broadest to narrowest.	Always in scope. Either a single .clinerules file or a .clinerules/ directory whose markdown files are all loaded.
Size limits	None	None	None
Measured — counted from real repositories on 2026-08-04
Repositories carrying it	179	33	79
Share of indexed repos	25.6%	4.7%	11.3%
Files indexed	1,280	46	305
Median length (words)	272	257	262
90th percentile length	1,170	1,704	1,412
Files naming commands	29.4%	52.2%	34.1%
Files containing code	58.0%	45.6%	33.1%
Median quality score	52	60	54
Median repository stars	24	11,320	1

How often they turn up together

A capability table cannot answer this at all. Of the repositories carrying the first format, this is the share that also carry the second — counted, both directions, on 2026-08-04.

GEMINI.md + Cline rules

2026-08-04

repositories carry both. That is 21.2% of everything with GEMINI.md, and 8.9% of everything with Cline rules.

Cursor rules + GEMINI.md

2026-08-04

repositories carry both. That is 6.1% of everything with Cursor rules, and 33.3% of everything with GEMINI.md.

Cursor rules + Cline rules

2026-08-04

repositories carry both. That is 7.8% of everything with Cursor rules, and 17.7% of everything with Cline rules.

What each one is for

Cursor rules

2026-08-02

The most expressive format here. Many small .mdc files, each with frontmatter declaring when it should load, so a rule about migrations only enters context when a migration is open. Costs the most to maintain and only one editor reads it.

Strengths

Glob-scoped activation — the only widely-used format that keeps unrelated rules out of context
Description-based activation lets the agent pull a rule in on demand
Many small files are easier to review in a PR than one growing document

Weaknesses

Cursor-only
Frontmatter is a schema, and a malformed .mdc silently stops applying
Fragmentation: rules spread over many files are easy to duplicate and contradict

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GEMINI.md

2026-08-01

Gemini CLI's memory file, structurally close to CLAUDE.md — @imports and a user-scope layer — which is why repos that carry both usually carry near-identical text in each.

Strengths

@path imports and a global user file, same composition model as CLAUDE.md
Explicit hierarchy from global to local

Weaknesses

Google-only
No glob targeting

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Cline rules

2026-08-01

A single file or a folder of files, all always-on. The folder form is the simplest way any format here lets you split rules into topics without also learning an activation model.

Strengths

Directory form splits rules by topic with zero configuration
Toggleable rule sets for switching context between tasks

Weaknesses

Cline-only
Everything is always-on — no targeting, so the folder form costs context

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