How do I write better prompts for an AI art API?

Be specific and layered: name the subject, then style, composition, lighting and mood. Keep prompts under the 2500-character limit, use a fixed seed when you want reproducible results, and iterate one variable at a time.

Can I reproduce the same image later?

Yes — pass the same model, prompt and seed. Omitting the seed (or using -1 where supported) produces a random result each run. Note that generated files are retained only temporarily, so download anything you want to keep.

Unfiltered AI Art API: Prompts, Limits & Best Practices

An unfiltered art API removes the gatekeeper, but it doesn’t write your prompts for you. The quality of what you get out of Api18.dev comes down to prompt craft and a handful of parameters. This is the practical playbook: how to prompt, how to make results reproducible, and which limits to design around.

Prompt structure that works#

Build prompts in layers, most important first:

Subject — who or what, concretely.
Style — photographic, illustration, 3D render, a named art style.
Composition — framing, angle, distance, what’s in shot.
Lighting & mood — time of day, light direction, color temperature.
Detail — materials, textures, small specifics that sell realism.

Iterate one variable at a time. Change the lighting or the composition between runs, not both — otherwise you can’t tell what helped.

Negative prompts

Where a model supports negative_prompt, use it to exclude what you keep getting by accident (extra limbs, watermarks, a style you don’t want). Check each model’s parameter list on the models page.

Reproducibility with seeds#

Pass the same model, prompt and seed to get the same image again. Omit the seed (or use -1 where supported) for a fresh result each time. Fix the seed while you tune a prompt, then unlock it to explore variations.

Aspect ratio & resolution#

aspect_ratio — match the destination: 1:1 for avatars, 9:16 for vertical, 16:9 for wide.
resolution — higher detail costs more; generate at a sensible size and upscale later if needed.
num_images — generate a small batch to pick from; cost scales per image.

Limits to design around#

Prompt length: up to 2500 characters — be specific, not endless.
Input images must be public URLs (for edit/image-to-video) — host first, then pass the URL.
Outputs are temporary — download and store anything you want to keep.
Lawful use only — unfiltered isn’t unlimited; illegal content is prohibited.

Put it to work#

Try prompts free with $10 of welcome credit in the playground. When you’re ready to integrate, the 5-minute quickstart gets you from key to image in one call.