We ran the 140 English prompts in the most-starred public Nano Banana collection on GitHub through a checker built from Google's own prompt guide. After a manual review, 12 of them (8.6%) broke one of the guide's hard rules, and 95 (68%) left at least two of style, light, framing and color for the model to decide. Those are curated prompts. The "Nano Banana prompt generators" that rank on Google are a mixed bag: some write prompts, some turn images into prompts, and several are image apps that sell credits. Here are the nine options worth knowing, what each one actually does, and how to check what it gives you.
The best Nano Banana prompt generators at a glance
The best Nano Banana prompt generators in October 2026, by job:
- PrompTessor: best overall for writing a prompt from an idea (free, no account).
- Gemini app: best for iterating where the image is rendered.
- nanobananaprompt.org: best for photo edits and figurine transformations.
- nanobanana.im Image to Prompt: best for turning a reference image into a prompt.
- Awesome-Nano-Banana-images on GitHub: best free library, organized by task.
- PromptEval image prompt checker: best for checking any of them against Google's guide.
A Nano Banana prompt generator is any tool that writes or rewrites the text instruction you give Google's Nano Banana image models. They fall into four groups: chat assistants, idea-to-prompt tools, image-to-prompt tools and prompt libraries. A checker is a fifth kind of tool that doesn't write the prompt but tells you whether it follows the guide.
| Tool | What it does | Free? | Login | Best for |
|---|---|---|---|---|
| PrompTessor | Idea → Nano Banana prompt, with reference roles and exact text | Free | No account to generate | Best overall for writing a prompt from scratch |
| Gemini app | Writes or refines a prompt in chat | Daily free quota | Google sign-in | Best for iterating in the same app that renders |
| ChatGPT, Claude and other assistants | Same, in their own chat | Free tiers | Account | People who already work in one of them |
| nanobananaprompt.org | Edit idea → prompt ("replace background with a sunset beach") | Free text box | None seen | Best for edits and figurine-style transformations |
| nanobanana.im Image to Prompt | Reference image → prompt, with Nano Banana as a target | Free | No gate on the page | Best image-to-prompt for copying a look |
| aisuperhub Image to Prompt | Image → prompt, JSON and a negative prompt | 4 credits per extraction | Not stated | Multi-model work (Midjourney, Flux, SDXL) |
| Awesome-Nano-Banana-images (GitHub) | Library of example prompts by task | Free, Apache-2.0 | None | Best library, organized by task |
| nanobanana.im prompt library | Trend templates (portraits, product, holidays) | Free to browse; credits to generate on the site | For generating | Seasonal and social templates |
| PromptEval image prompt checker | Checks any prompt against Google's guide and fixes what it can | Free | None | Best for checking whatever the other tools give you |
How we evaluated them
Every option got the same four questions, answered on October 29, 2026: what it actually produces, whether it's free and whether it needs a login, whether its output follows Google's six prompting rules (we ran each tool's own published example through our checker where one was available), and what goes wrong in practice. The rules come from Google's guides, listed in the next section, so you can repeat the check on any tool, including ones we didn't cover. What we didn't do: create accounts or run paid generations on any of these sites, so where a tool publishes no example, we describe what its page offers and say so.
What Google's guide asks for (use this to judge any generator)
Google publishes Nano Banana prompting advice in two places: the ultimate prompting guide for Nano Banana on the Google Cloud blog (March 2026) and DeepMind's image prompt guide. A good generator's output should pass every row of this table:
| Rule | What Google says | Typical generator slip |
|---|---|---|
| Narrate the scene | "A simple list of keywords won't cut it." Formula: [Subject] + [Action] + [Location/context] + [Composition] + [Style] | Comma lists of tags: "cute, pastel, 4k, trending" |
| Say what you want | "Describe what you want, not what you don't want": "empty street" instead of "no cars" | "No people, no text, no blur", or a separate negative prompt |
| Quote exact text | Enclose the words in quotes and describe the typography | "Add a title" with no wording, so the model invents letters |
| Edits: say what stays | "Be explicit about what to keep exactly the same" | "Make it better" with no keep-clause |
| References | Up to 14 reference images; give each character or object a distinct name | "Combine image 1 and image 2" without saying what comes from each |
| Aspect ratio | In the app, write it in the prompt (4:3, 1:1, 9:16); in the API, set aspect_ratio in the request | "8K, ultra HD" in the text, which sets nothing |
One model detail matters before you copy any older prompt: in the Gemini API, Google now recommends Nano Banana 2.1 (gemini-nano-banana-2.1, released October 6, 2026) for new projects, and Nano Banana Pro for the most complex scenes. In the Gemini app, Nano Banana 2 is the default. The rules above apply to all of them.
What 140 popular prompts get wrong
To see how often curated prompts break these rules, we took every English prompt from PicoTrex/Awesome-Nano-Banana-images, the largest Nano Banana prompt collection on GitHub (23,964 stars on October 29, 2026, Apache-2.0), and ran them through our checker set to Nano Banana in the Gemini app. Then we read every hard-rule hit by hand and kept only the clear ones.
| Issue | Prompts (of 140) | Share |
|---|---|---|
| "No…" or "avoid…" phrasing instead of a positive description | 6 | 4.3% |
| Text requested in the image without the exact words in quotes | 3 | 2.1% |
| Prompt written as a keyword list | 2 | 1.4% |
| Photo edit that doesn't say what to keep | 1 | 0.7% |
| Any hard-rule issue | 12 | 8.6% |
| Missing at least two of style, light, framing, color | 95 | 68% |
Two readings. First, curated prompts mostly follow the hard rules; the classic mistake that survives curation is the negative ("Avoid neon colors", "No extra people"), which is exactly what Google's guide tells you to rephrase. Second, the 68% figure overstates the problem for edits: "turn this photo into a figurine" doesn't need a lighting note, because the source photo already has one. For new images it's the main lever, since every missing layer is a decision the model makes differently on each run.
A note on method. The first pass of our own checker flagged 39 hard-rule issues, many of them wrong: it read "No text." as a request for text and missed roles given inline, like "the makeup from Image 2". We fixed those rules before counting. The fixed checker flagged 18, and the 12 in the table are the ones that held up under manual review.
From a rough idea to a prompt that passes
Most people start with something like the draft below: a string of tags typed in a hurry. Run through the checker with Nano Banana in the Gemini app selected, it gets three flags.
Draft · 24 words · 3 flags
| Flag | Why Google's guide objects | Fix |
|---|---|---|
| Text without quotes | "Morning Ritual" isn't marked as exact words, so the model may invent the lettering | The label reads "Morning Ritual" in a dark green serif font |
| Keyword list | "A simple list of keywords won't cut it" | Write it as two or three sentences |
| "No clutter, no people" | Naming what you don't want can pull it in | "A clean counter with only the bag and the cup" |
After · 80 words · 0 flags in the Gemini app
The "4k" is gone because it sets nothing; in the app, resolution is a dropdown. "Vertical 4:5 format" stays, since DeepMind's guide tells you to prompt for the aspect ratio in the app. Through the API, the checker moves "4:5" into the aspect_ratio setting instead.
Each option, and when it's the right one
PrompTessor: best overall for writing from scratch
The top result for this search in late October 2026, and the most carefully built page we read. You type what you want, pick an output language, and get a full prompt back without creating an account. Its Nano Banana page links Google's Gemini image generation and image prompting guides as sources and shows a last review date (September 5, 2026), and its prompting advice matches Google's: describe the image in natural language, explain each reference image's role, quote exact text, and protect what an edit shouldn't touch. We ran its own published example (a launch poster with a character reference and the headline "CREATE WITHOUT LIMITS") through our checker: it passed all six checks.
Drawbacks: saving prompts, history and its analysis and optimization tools need a free account. It covers dozens of models, so the Nano Banana specifics live in one page section rather than a dedicated tool.
Gemini and other chat assistants
Google's Cloud blog guide says Gemini can help you create prompts and with creative direction, and it's the shortest path from "a cozy coffee ad" to a full scene description. The catch is that chat assistants happily write "no clutter, no text" or a tag list if you ask loosely. Ask for one narrative paragraph that follows subject, action, location, composition and style, with any on-image words in quotes, and you get much closer on the first try.
nanobananaprompt.org
A single text box built around edits: you describe the change ("replace background with a sunset beach", "turn into a 1/7 scale collectible figure") and it returns a prompt. It suits photo transformations, which are what Nano Banana is most often used for. Read the result for a keep-clause before using it; an edit prompt without "keep the face, pose and lighting" is where identity drift starts.
Image-to-prompt tools
nanobanana.im's Image to Prompt is free and lists Nano Banana as a target; aisuperhub's version charges 4 credits per extraction and targets several models at once. Both are handy when you have a reference and want words for it. Watch for one thing: tools built for many models often add a negative prompt section. Google's docs describe no negative prompt field for Nano Banana, so those lines either get ignored or, worse, name the objects you wanted gone. Rewrite them as positive descriptions.
Prompt libraries
The GitHub collection above is the best free starting point: organized by task, licensed Apache-2.0, and, by our count, mostly clean on the hard rules. nanobanana.im's library leans toward seasonal and social templates and sends you to its own paid generator to render them. Libraries are where you'll find the longest prompts (the GitHub set averages 65 words), so trim what doesn't apply to your image.
A checker for whatever you end up with
Apart from PrompTessor, none of the third-party generators we checked mentions Google's guide. The PromptEval image prompt checker runs the six rules from the tables above in your browser, rewrites what it can (quotes around detected text, negatives swapped for positive phrasing, settings moved out of the text in the API) and tells you what only you can decide. It also covers GPT Image 2.5 and Midjourney V8.2, whose rules differ in the places that matter most (table below).
Drawbacks: it doesn't write a prompt from a blank idea, and it can't see your reference images, so it can't tell whether the role you gave each image makes sense. Its rules are pattern checks: our own audit above found false positives before we fixed them, and some will remain.
| Nano Banana | GPT Image 2.5 | Midjourney V8.2 | |
|---|---|---|---|
| Excluding things | Describe the positive ("empty street") | "No watermarks"-style lines appear in OpenAI's own examples | The --no parameter at the end |
| Exact text | In quotes, with typography | In quotes, with placement and how many times it appears | In double quotes; single quotes don't work |
| Aspect ratio | In the prompt (app) or aspect_ratio (API) | size in the API | --ar 16:9 at the end |
Which tool for which job
| You have | Use | Then |
|---|---|---|
| A vague idea | Gemini or another assistant, asking for one narrative paragraph | Check it; add light and framing if missing |
| A reference image | An image-to-prompt tool | Delete any negative prompt lines; rewrite them as positives |
| A photo to edit | nanobananaprompt.org, or write it yourself | Add what must stay the same: face, pose, lighting |
| Words that must appear | Any of the above | Put the exact words in quotes, with font and position |
| No idea where to start | The GitHub library, by task | Swap in your subject and trim the rest |
The same habits carry over to video: our guide to Veo 3 prompt mistakes shows how Google's video guides handle negatives and dialogue, and prompt format for Claude, GPT and Gemini covers the text side. For the general skill of replacing vague words with concrete ones, see how to write specific AI prompts.
Frequently asked questions
What is the best Nano Banana prompt generator?
For turning an idea into a prompt, PrompTessor's free Nano Banana generator is the strongest option we found: no account, it links Google's official guides, and its published example passes all six checks of Google's rules. For recreating a look from a picture, nanobanana.im's free Image to Prompt works. Whatever you use, check the result against Google's rules (narrative description, no "no", exact text in quotes) before you spend a generation.
Is there a free Nano Banana prompt generator?
Yes. As of October 29, 2026, nanobanana.im's Image to Prompt is free with no login gate on the page, nanobananaprompt.org has a free text box that turns an edit idea into a prompt, and the Awesome-Nano-Banana-images collection on GitHub is a free, Apache-2.0 library of example prompts. The Gemini app can write prompts too, within its daily free quota, but it requires a Google sign-in.
How should a Nano Banana prompt be written?
Google's guide recommends a narrative description following [Subject] + [Action] + [Location/context] + [Composition] + [Style], not a list of keywords. Describe what you want instead of what you don't ("empty street" rather than "no cars"), put any words that must appear in the image inside quotes, and when editing a photo say explicitly what must stay the same.
Which Nano Banana model should I use in October 2026?
In the Gemini API, Google's docs recommend Nano Banana 2.1 (gemini-nano-banana-2.1, released October 6, 2026) for new projects, with Nano Banana Pro (gemini-3-pro-image) for the most complex visual tasks. In the Gemini app, Nano Banana 2 is the default, with Nano Banana Pro on paid plans.
Do Nano Banana prompt generators follow Google's guide?
Only one of the third-party generators we checked, PrompTessor, links Google's official guides on its page. Others produce output that contradicts the guide, such as a separate negative prompt, which Google's docs don't describe for Nano Banana. Treat generator output as a draft: run it through a checker built on Google's rules, or review it against the guide yourself.