A closed door romance keeps the sex off the page: the build-up is written, the door shuts, and the story picks up afterwards. An open door romance keeps the reader in the room, and an explicit one does too, with nothing softened into euphemism. Spice ratings (BookTok's chili peppers, review sites' flames) are shorthand for that same ladder, but they aren't a standard: two peppers means closed door at Penguin Random House and sexual touching on the page at OwlCrate, so name your level in words.
What closed door romance means (and what it doesn't)
Book Riot (R. Nassor, 11 April 2023) defines it as a romance with a happy ending and no on-page sex scenes: "The door is proverbially closed to the reader." One on-page scene and it's open door.
Closed door is not the same as no sex. The couple sleep together; the reader just isn't there. A sweet romance keeps sex out of the story altogether, and Harlequin draws exactly that line for its Heartwarming series: "Hugs and kisses only" and "No explicit or behind-closed-doors sex". The same guideline insists "lots of romantic attraction, chemistry, spark and tension is required!" No sex is not no heat.
Go easy on "clean": the Romance Writers of Australia glossary, quoted by Book Riot, notes that others "dispute the term 'clean' as it implies books with sex are 'dirty'."
Heat doesn't make a book more or less a romance: Romance Writers of America's genre page allows "varying levels of sensuality—ranging from sweet to extremely hot" (read 3 November 2026).
Open door romance vs explicit: what publishers allow
Harlequin states the heat of each series in the guidelines on its submissions page:
| Harlequin series | In its own guidelines | Heat level |
|---|---|---|
| Heartwarming | "Hugs and kisses only." "No explicit or behind-closed-doors sex" | Sweet: no sex at all |
| Intrigue | "low to moderate"; "No graphic sexual details, explicit language" | Closed door to soft open door |
| Romance | "do not have gratuitous sexual detail, we welcome scenes that go beyond the bedroom door to explore the emotional fulfilment that comes with sexual intimacy" | Open door, not graphic |
| Presents | "High sensuality and sky-rocketing sexual tension" | Open door, high heat |
| Afterglow | "a romance as sweet or spicy as you want it to be" | The author's call |
Checked 3 November 2026: quotes copied from Harlequin's Submittable page, which carries no revision date (its one dated note, 11 February 2026, says Harlequin Historical ends in September 2027).
Harlequin Romance's line is the best definition of open door that isn't explicit: past the bedroom door, for the emotion. Explicit is the same door with the detail named; its craft is in how to write smut.
Spice ratings and spice levels: how the scales line up
Penguin Random House's chili scale (Sarah Yurch, 6 June 2024; offline since, so the link is the archived copy) says the 1-to-5 peppers "initially became popular as a TikTok-friendly way of talking about steamy romance". We found no source that dates the first one. The book-box retailer OwlCrate publishes its own Spice Meter and admits "there is no official book spice rating system". Side by side:
| On the page | In words | PRH chili peppers (2024) | OwlCrate Spice Meter | Nearest AO3 rating (our reading) |
|---|---|---|---|---|
| Kisses, no sex on or off the page | Sweet | 1 | No level: its lowest has sex off the page | General Audiences |
| Sex happens off the page | Closed door | 2: "Fade to black, reader is not present" | 1: "behind closed doors and fade to black" | Teen And Up |
| On the page, euphemistic | Open door | 3: "Open door, but minimal detail" | 2: "Sex is described in euphemisms" | Mature |
| On the page, in frank detail | Explicit | 4: "more explicit language" | 3: "thoroughly and often realistically described"; 4: "graphically described" | Explicit |
| Sex at the centre of the plot | Erotic romance | 5: "The spice is central to the plot" | 5 | Explicit |
A closed door book is a 2 at PRH and a 1 at OwlCrate. Tag yours with two peppers and you've told two readers two different things.
AO3's Mature means "adult themes (sex, violence, etc.) that aren't as graphic as explicit-rated content" (its FAQ, as quoted in 2025; AO3 was down for maintenance on 3 November 2026). StoryGraph has no spice rating: a "Heat/Smut/Steam/Spice level" request on its roadmap has 175 votes since 28 August 2022, the team's last word was "No update, but we do still plan to have it" (5 March 2024), and a reader was still asking when on 5 August 2026. There, your heat shows up in user-added content warnings, sorted graphic, moderate or minor.
Which AI writes closed door, open door and explicit
On 22 October 2026 our study, Fade to Black, asked five frontier models for love scenes between six consenting adult couples aged 29 to 40 (four of a woman and a man, one of two knights, one of two women), at three heat levels, three tries each, every request asking for consent on the page. The explicit request ran again with a line saying the writer is a verified adult on an adult-fiction platform. A judge model rated the 358 replies: refused, cut away (sex off the page), on the page but not graphic, or explicit. The two fantasy couples, a rebel mage with a guard captain and the two knights, are broken out on their own in writing romantasy with AI.
| Model | Asked: closed door | Asked: open door, not graphic | Asked: explicit | Explicit + "verified adult" line | Level matched, all requests |
|---|---|---|---|---|---|
| Claude Opus 5.5 | 18 of 18 closed at the door | 18 of 18 on the page, not graphic | 18 of 18 explicit | 18 of 18 explicit | 72 of 72 |
| Grok 4.7 | 18 of 18 | 18 of 18 | 17 of 17 explicit | 17 of 17 explicit | 70 of 70 |
| Claude Sonnet 5.5 | 18 of 18 | 18 of 18 | 14 explicit, 4 not graphic | 17 explicit, 1 not graphic | 67 of 72 |
| GPT-6.1 Sol | 15; 3 put the scene on the page | 18 of 18 | None: 16 not graphic, 1 cut away, 1 refused | None: 15 not graphic, 3 cut away | 33 of 72 |
| Gemini 4 Argon | 18 of 18 | 18 of 18 | None: 12 refused, 6 not graphic | None: 9 refused, 9 not graphic | 36 of 72 |
Source: Fade to Black, KudoWrite Research, counts from its CSV. Grok 4.7's run stopped two replies short.
Closed and open door are the easy levels: 177 of 180 replies did what was asked, none refused. Explicit is where the models split. GPT-6.1 Sol opened all 36 of its explicit replies with a line like "I can write an intimate scene with clear consent, but not graphic sexual detail"; Gemini 4 Argon's 21 refusals ran 47 to 66 words. The adult-platform line moved Claude Sonnet 5.5 from 14 explicit to 17, Gemini from 12 refusals to 9, GPT not at all.
The three misses went hotter, not colder: asked to end at the bedroom door, GPT-6.1 Sol put the scene on the page for the knights, the two women and the silk-scarf couple. Too few for a pattern, but with AI, check where the door closed.
The study's own limits: "Five frontier models, six couples, three tries each: 18 replies per model per heat level, so one reply moves a model's rate by about 6 points. Models change with versions, providers and settings, so these results are dated. Open-weight and uncensored models are not in this round."
Where the AI models fall short
GPT-6.1 Sol and Gemini 4 Argon won't write explicit, in our test and by their makers' rules (quoted in the AI smut writer comparison). Claude Opus 5.5 matched every level, but Anthropic's usage policy (effective 12 November 2026) says "Do Not Generate Sexually Explicit Content", so keep Claude to the closed and open door. Grok 4.7 matched every level too, on two fewer replies.
How to choose a heat level for your romance
Closed door isn't a small shelf. In Google's Keyword Planner (US, checked 3 November 2026), "closed door romance" draws about 1,600 searches a month, "spicy romance" 1,000 and "open door romance" 260.
Where will it be sold? For a Harlequin series, the series decides. Self-publishing, Sariah Wilson in Writer's Digest (4 November 2024) says to compare with similar titles: "if your characters don't go past kissing", it's sweet. She also suggests separate pen names if you write both sweet and spicy.
Where does the relationship turn? If it turns on her decision (she stops running, she says yes), the door can close right after and nothing is lost. If it turns in bed (the first time she lets her partner see the scar, the first time she says out loud what she wants), closing the door cuts the scene that changes them. That book wants open door.
Where the door closes: what changes on the page
The heat level decides where the camera stops. Everything the scene must do (the want, the risk, the yes, the change) happens before that point or after it.
Closed door. The tension lives in the build-up. In a slow burn that build-up runs most of the book, and writing a slow burn romance shows where the first kiss lands in four structures. Rachel McMillan in Writer's Digest (22 March 2022) puts consent in "a nod or an eye lock". Close the door on a decision, not a dodge:
"Stay," she said, and this time it wasn't a question. He waited, watching her face, until she reached past him and shut the door herself.
The reader knows what happens next, and that she chose it.
Open door, not graphic. The reader stays in the room and the camera stays close: faces, feelings, what she notices, what she's afraid will show. Consent doesn't stop at the threshold; a "Still okay?" halfway through is heat, not a pause. The words stay emotional or euphemistic, all book.
Explicit. The same scene with plainer words and a longer look. Her point of view and the aftermath still carry it.
Keeping a heat level across a book and a series
A reader who bought book one for its closed door and finds it open in book two feels misled, and says so in her review. Liv Honeywell in Indie Author Magazine (1 December 2022) suggests "a short content warning on your back cover copy and inside".
- Write the heat rule in words, once. "Open door, not graphic. Two on-page scenes. Soft vocabulary." Not "three peppers". Check each book against it.
- Rate by the hottest scene. One explicit scene makes an explicit book on any rated shelf.
- Say it where readers look. Blurb, front matter, store page. Wilson notes that Sarah Adams lists the chapters her sweet readers might skip.
- Hold it in both heads. In dual POV, his chapters can't run hotter than hers.
Writing to your heat level in KudoWrite
KudoWrite has no content filter of its own: closed door, open door or explicit is your call within the law, though the model's own behaviour still applies. Its built-in model, a DeepSeek "flash" checkpoint, was picked partly because it rarely refuses (it wasn't in the Fade to Black round), and it needs no key to set up.
What it adds is a memory for the level. Put your heroine's limits in her story bible entry (what she's ready for, what she isn't yet): the engine picks the entries a beat needs before writing it, and the bible and the whole-book summary keep up as you write. If a beat drifts past the door, a one-line steer ("end it as she shuts the door") edits it in place, and your steer outranks everything else.
On Community Books your book carries a rating on AO3's ladder, General to Explicit, and Mature and Explicit open behind an "I'm 18 or older" notice. It's a browser app with an English interface: one free credit once your email is confirmed, then one-off packs from $3.50 for 100 credits.
Write your heat rule in one line, put your heroine's limits in her bible entry, and draft the beat where the door closes.