Ranbooru Prompt

Ever sit staring at an empty prompt box wondering what a good "1girl" scene actually looks like in tags? This node is the answer to that specific laziness. Ranbooru Prompt searches a booru site's API for real posts matching your tags, grabs one post's tag list, and hands it back to you as a ready-to-use positive (and optional negative) prompt. No API key, no scraping setup, no database - it's a direct port of the popular sd-webui-ranbooru plugin that Forge users rave about, rebuilt as a single ComfyUI node. If you run any of the anime SDXL family (Illustrious, NoobAI, Pony) you already know those models think in Danbooru tags, so a node that hands you professionally-tagged posts is cheating in the good way.

How it works

The mechanism is simple and honest. You give it a search, it hits the chosen booru's JSON API, and pulls a page (or pages) of posts. Each site has its own scraper class - gelbooru, danbooru, rule34, e621, safebooru, konachan, yande.re, aibooru and xbooru are all supported. Then it:

• picks one post, by sorting_order (a true random pick, or a score-weighted pick biased toward the top or bottom),
• shuffles that post's tag list (order matters - earlier tags get stronger attention, so randomizing is the point),
• strips out a built-in blocklist of junk tags like watermark, text, signature, censored and even ai_generated / stable_diffusion (you can add your own via remove_tags),
• applies your background/color strategy, truncates to your limits, and emits positive and negative strings.

The output is just text, so the wiring is dead simple: Ranbooru Prompt → CLIPTextEncode → KSampler. Two STRING outputs, both clean.

The inputs that matter

There are a lot of knobs and most of them are "leave alone until you care." The ones a beginner actually touches:

• booru - which site to search. Default safebooru, which is conveniently the one you can point at work.
• tags - comma-separated, exactly like you'd type them into the site (1girl,long_hair). Required; an empty search is a coin flip.
• mature_rating - maps to each site's rating scheme (Safe/Questionable/Explicit on rule34, the g/s/q/e single-letter scheme on danbooru/gelbooru). Keep it All and you will eventually get something awkward.
• shuffle_tags and change_dash - shuffle randomizes tag order each run (that's your variety); change_dash swaps _ for spaces, which is the "always replace underscores" rule from the prompting guides, automated.

The less obvious ones: sorting_order (Random / High Score / Low Score), limit_tags and max_tags to trim how many tags survive, and post_id to pin a specific post. mix_prompt blends tags from 2–10 posts, which is genuinely fun for pulling together a vibe from several images.

The negative prompt catch

Worth knowing up front: the negative output is empty string unless you turn on chaos_mode. Set it to Chaos or Less Chaos and the node splits your tag list - some tags go to the negative prompt, which is a quick way to fight against whatever composition you don't want without writing a word. Otherwise it's empty, so don't panic that you broke something.

Install

The easy way: ComfyUI Manager → search "ComfyUI-Ranbooru" → install → restart. Or by hand:

cd ComfyUI/custom_nodes
git clone https://github.com/liming123332/ComfyUI-Ranbooru

then restart ComfyUI. The only hard dependency is requests, which ComfyUI already ships, and the install script auto-installs the optional requests_cache - the node's use_cache defaults to on, so let that finish or you'll sit through the same API calls every single run. There are no model files to download; this thing only fetches tags, not images.

Troubleshooting

The README owns its real failure modes. Same prompt every run? Check three things: no post_id, sorting_order is Random, and shuffle_tags is on. Rule34 returns nothing? The node automatically retries without the default -animated exclusion, but some searches genuinely have no hits. Network errors like WinError 10054? That's the API resetting your connection - retry or switch networks; this is a live-HTTP node, so it's only as reliable as your connection to e621.

One quirk that'll bite you: when a search finds zero posts, the node returns a literal Chinese string ("未找到符合条件的帖子") as your positive prompt instead of an error. If your prompt suddenly becomes CJK, that's not a bug - your tags just matched nothing. Loosen the tags or lower max_pages, and remember mature_rating: All on safebooru is the most forgiving setting for a first run.