For more control over an AI-generated image, describe the result you want in plain, specific language: its purpose, subject and action, setting and composition, important visual qualities, and any constraints. Begin with the essentials, then refine one mismatch at a time. This guide is about prompting a generator; writing accessible alt text for an image that already exists is a different task, covered below.
Build a prompt around the decisions that matter
A useful prompt gives the generator enough direction to make the image fit your goal, without burying that goal in a long list of adjectives. OpenAI Academy puts it simply: “A good image prompt does not need to be long.” It recommends starting with one to three clear sentences about purpose, subject, action, setting, and visual style. OpenAI Academy’s image-prompting guide
Use this flexible checklist to decide what to include. You do not need to fill every category for every image.
- Purpose: What should the image do—a product photo, event poster, diagram, editorial illustration, or something else?
- Subject and action: Who or what is central, and what are they doing?
- Scene and composition: Where is the subject? What belongs in the foreground or background? Specify framing, camera angle, placement, or empty space if those affect the result.
- Visible qualities: Name important colors, materials, textures, lighting, and style. Prefer concrete details such as “matte black ceramic” or “soft window light” when those distinctions matter.
- Constraints: Say what must remain, what should be excluded, any exact words to show, and practical layout requirements such as space for a headline.
For example, instead of “a nice coffee picture,” try: “Create a square product photo of a white ceramic mug on a pale oak table, with a small pour of coffee beside it. Use soft morning window light and a quiet neutral background; leave open space in the upper-right corner for a label.” The purpose, subject, lighting, and layout are explicit, while details that do not affect the intended result are left open.
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Write in whichever format is easiest to read and revise. OpenAI’s API guide recommends maintainable prompt formats rather than requiring special syntax. OpenAI API image-generation guide
Make composition and constraints explicit
When a result feels close but not usable, the missing instruction is often about where things go, what must be visible, or what must not change. Describe spatial relationships in ordinary language: “the person stands to the left of the bicycle,” “the label faces the camera,” or “keep the background uncluttered.” If the image needs room for copy, say where that room should be.
For multiple reference images, identify each one and explain its role rather than assuming the generator will infer it. For example: “Use the first image for the bottle shape and the second for the lighting; keep the label text from the first image unchanged.” Specify which elements to preserve and which to adapt. Spatial language is particularly useful when the relationship between subjects matters.
Text, posters, and dense layouts
If words must appear inside the image, quote the exact text and specify its placement and appearance—such as font style, size, and color. Keep the requested copy short where possible, then inspect the output carefully. OpenAI Academy recommends concise text and suggests emphasizing legibility for dense layouts; a design tool may be needed to polish or correct the final typography. OpenAI Academy’s image-prompting guide
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For diagrams and infographics, check every label and factual relationship. A visually convincing rendering does not establish that its data, labels, or connections are correct.
Refine one mismatch at a time
- Generate a first pass using the core idea, composition, and most important visual qualities.
- Name one concrete mismatch. For instance, the background is too busy, the light is too dark, or the subject is in the wrong part of the frame.
- Request one targeted change instead of rewriting the whole prompt. OpenAI Academy gives examples such as brightening an image or simplifying its background.
- Restate details that must stay stable when making the edit—for example, preserve the subject’s pose and the label while changing only the background.
- Review the result against your purpose and constraints, then repeat only if another specific change is needed.
This small-edit loop makes it easier to see what each instruction changes. For reference-based work, keep describing which image contributes which feature and what should remain unchanged.
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Adapt your wording to the generator
There is no universal prompt formula. Providers give different advice, and model outputs can differ, so use the current guidance for the generator you have selected and judge the result with your own inputs.
| Generator guidance | What its official material recommends |
|---|---|
| OpenAI image generation | Use readable, maintainable prompts; outputs can vary by model, so test techniques with the actual model and inputs. OpenAI API image-generation guide |
| ChatGPT image prompting | Start with a short, clear description and refine with targeted edits. OpenAI Academy’s image-prompting guide |
| Adobe Firefly | Use direct descriptive language, naming the subject and relevant descriptors. Adobe’s help page was last updated June 9, 2026. Adobe Firefly prompt-writing guidance |
| Runway Gen-4 | Its guide recommends full sentences for greater control over certain elements and says detailed prompts can offer fine-tuned control. Runway Gen-4 prompting guide |
| Google Imagen | Consult Google’s official prompt guidance for the relevant Imagen workflow. Google Imagen prompt guide |
The table summarizes provider guidance, not a head-to-head performance ranking. Prompt controls, reference handling, and consistency are specific to the tool and model you use.
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Image-generation prompts are not alt text
A generation prompt tells a system what image to create or edit. Alt text serves a reader who may not see an existing image, so it should convey the information or function that matters in context—not simply inventory everything visible.
- Informative image: Give a concise description of its essential information.
- Decorative image: Use an empty text alternative when the image adds no information or function.
- Functional image: Describe the action or destination, such as what a linked image does.
- Complex image: Provide a complete text equivalent for information that cannot be conveyed adequately in a short description, as with a graph or diagram.
These categories follow the W3C Images Tutorial. The right alternative depends on the image’s purpose and surrounding content.
When describing an existing image outside a generation prompt, X’s writing guidance recommends focusing on important visible details, being concise and objective, including relevant text and image-type details, and avoiding claims about events or motives that the image alone cannot confirm. X’s image-description guidance
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