If Nano Banana Pro says "Unsupported file URI type" or "Invalid or unsupported file uri," the first fix is not a better prompt. It is to check what kind of file reference you passed and which Gemini surface rejected it.
Native Gemini file_data, OpenAI-compatible image_url, Vertex gs:// paths, public HTTPS objects, and local file paths do not share one URI rule. A public URL is not a Gemini file resource, a local path is not a reusable file URI, and a data: URL belongs only on the compatibility route that explicitly accepts image_url.
Start by splitting the failure into four branches. If you are on native Gemini, upload first or use files.register for a supported GCS route, then reuse the returned file resource. If you are on the OpenAI-compatible route, keep the documented image_url shape and rebuild a clean base64 data: payload. If you passed a public URL or a local path as if Gemini could fetch it later, stop and move that input onto the route that surface actually supports.
After the smallest route fix, retry on the same surface and verify that the same request now accepts the file. If it still fails after the route is clearly correct, stop blaming the model and inspect payload integrity, expired resources, or wrapper behavior next.
30-Second Route Board
The working rule is simple: this error is usually about the file route, not the model prompt. Current Gemini docs were rechecked on April 9, 2026, and they still separate native Files API uploads, files.register for GCS objects, and OpenAI-compatible image_url payloads into different contracts.
Use this board before you retry anything:
| What you passed | Most likely problem | Safest first action | Verify on the same surface | Escalate when |
|---|---|---|---|---|
| Public HTTPS URL | You treated a public object like a native Gemini file resource | Upload it through the Gemini Files API, or register the underlying GCS object if that is your real source | The same request now accepts the file on the same Gemini route | The returned file resource still fails |
data:image/...;base64,... | You are either on the wrong surface or the base64 string was malformed in transit | Stay on the OpenAI-compatible route and resend a clean image_url payload | The same compatibility request now accepts the image | A clean payload still fails on the same compatibility route |
gs://bucket/object | You mixed native Gemini and Vertex behavior | On Gemini, use files.register; on Vertex, keep the Vertex-specific gs:// route | The same surface now accepts the object | The same docs-aligned cloud route still fails |
Local file path such as /tmp/x.png or file:///... | Your app sent a device path as if Gemini could fetch it later | Upload the file first and reuse the returned resource | The same flow now uses a valid file resource | Uploaded files still fail or your wrapper rewrites the request |
If you only remember one thing from this page, remember this: a valid image format does not guarantee a valid file route. Gemini's current image docs list PNG, JPEG, WEBP, HEIC, and HEIF as supported image types, but the error on this page usually appears before the model gets a usable file resource at all.
If You Are Using Native Gemini file_data
Native Gemini wants a Gemini File resource or another first-party route the current docs explicitly support. It does not want an arbitrary public URL or a raw filesystem path pasted into file_uri. That is why this error often shows up even when the image itself is a perfectly normal PNG or JPEG.
The fastest fix is to upload first. Gemini's current Files API docs say the native workflow is: upload bytes, get a returned file.uri, then reuse that returned file resource in the generate call. If your source file already lives in Google Cloud Storage, the current Files API reference now documents files.register, which can register a GCS URI and give you a File resource without pretending a public URL is already one.
That matters because a lot of older forum advice was directionally helpful but operationally incomplete. You will still find threads telling people that AI Studio or Gemini cannot use GCS directly and that gs:// belongs to Vertex only. That older distinction is still useful as a warning against route confusion, but it is no longer the whole current story. The official 2026 contract is narrower and more useful: on native Gemini, do not pass a public or local path as if it were already a file resource. Upload it or register it first, then reuse the resource the API gives back.
There is also a lifecycle detail worth keeping in mind after the immediate fix. Gemini's current Files API docs say uploaded files are stored for 48 hours. So if the same request used to work and now suddenly fails, do not assume your prompt broke. Check whether you are reusing an expired file resource instead of refreshing the upload or registration step.
If your larger problem turns out to be broader request validation, model overload, or quota rather than file routing, stop here and switch to a broader guide. Our Nano Banana Pro error codes guide is the better follow-up once the request has clearly moved beyond this exact URI-routing symptom.
If You Are Using OpenAI-Compatible image_url
This is the branch that confuses people most because the same error string can appear even when the route itself is conceptually correct. Gemini's current OpenAI compatibility docs show multimodal image inputs using image_url, including base64 data:image/...;base64,... values. So data: is not universally unsupported. It is just surface-specific.
That means the first question here is not "does Gemini support data: URLs?" The current answer is yes on the compatibility route. The better question is "did my pipeline preserve the payload exactly as that route expects?" A malformed base64 string, an HTML-escaped payload, a wrapper that rewrites your content items, or a compatibility client that quietly mutates the request can still trigger the same unsupported-file-URI family of errors even though the published route is valid.
Treat this branch as a payload-integrity check after you confirm the route. Keep the documented image_url shape, regenerate the base64 from the original file, and resend the request without additional transformation steps. Do not "fix" a compatibility payload by copying native Gemini file_data logic into it. That usually creates a second error on top of the first one.
The reason this section exists as its own branch is that exact-error forum threads already show how misleading the symptom can be. One current Google AI Developers Forum thread reproduces the literal Unsupported file uri: data:image/png;base64,... message, even though the official compatibility docs still support data: image payloads. The practical lesson is not "the docs are wrong." It is "the same error can come from a corrupted or transformed payload after the route choice was already correct."
If you are not sure whether you are on the compatibility route or the native Gemini route, stop and identify that first. The two surfaces can talk about the same image input using different contract language, and mixing them usually produces exactly the kind of confusion that led you here.
If Your Input Is a GCS Object, Public URL, or Vertex Path
Public URLs, registered Gemini files, and Vertex gs:// objects are not interchangeable. This is the part that many short forum answers get half right and then leave unfinished.
If you are on native Gemini and you passed a public HTTPS object URL, you probably treated a fetchable object as if it were already a Gemini File resource. That is the wrong mental model. A public URL may be reachable in a browser and still be invalid in native Gemini file_data. The right repair is to upload it through the Files API or use files.register when your true source of record is a GCS object. The registration route is about the storage object itself, not the public web wrapper URL.
If you are on Vertex AI, the route logic is different. That is the one branch where a gs://bucket/object reference can be the expected native shape. The mistake is carrying that assumption back into native Gemini or AI Studio and expecting every Google-branded image route to share the same object contract. They do not.
The practical fix is to ask one narrow question: which surface owns this request right now? If the answer is native Gemini, move toward File API upload or files.register. If the answer is Vertex, keep the Vertex-specific object route. If the answer is "I only pasted a public URL because it looked URI-like," stop there and convert it into a real file resource before retrying.
This is also why broad claims like "GCS never works on Gemini" are now too blunt to publish. Older threads captured real reader pain, but the current official contract is more nuanced. Native Gemini still does not treat arbitrary public URLs as ready-made file URIs. At the same time, the current API reference does expose files.register for GCS-backed workflows. That is exactly the kind of update a narrow troubleshooting page should preserve.
If Your App Passed a Local File Path
Local and mobile path errors look deceptively reasonable because the input often already points to a real file on your device. But /tmp/example.png, file:///storage/emulated/..., and similar device paths are local references for your app, not reusable file resources that Gemini can fetch later on demand.
The safest cross-platform rule is to upload first. Once the file has become a Gemini-managed resource, you can reference the returned URI the way the current docs expect. Until then, your path only proves the file exists on your side of the boundary. It does not prove the Gemini surface you are calling can dereference it.
This is where mobile and wrapper-specific examples can waste a lot of time. You may find narrow discussions about content:// behavior or client-library exceptions. Some of those edge cases are real, but they should stay secondary. If you build your recovery around one SDK quirk before you fix the primary route, you are likely to end up with an article-shaped detour instead of a working request.
So the right order is: upload first, confirm the returned file resource works on the same surface, then revisit client-specific URI nuances only if the problem survives that first-party route correction. That keeps the page useful for readers on Android, local desktop tooling, and wrapper libraries without turning the whole article into one platform deep dive.
If your real failure is broader than this exact route problem after the upload succeeds, our Nano Banana Pro troubleshooting hub is the better next stop because it covers the larger error families this page intentionally avoids.
Verify the Fix and Catch the Remaining Edge Cases
Once the request starts working again, do not stop at "the error disappeared once." Verify the fix in the same environment that failed before:
- Retry on the same surface after one minimal route correction, not after a full workflow rewrite.
- Confirm the same request now accepts the file and that the output matches the job you were actually trying to run.
- If you uploaded or registered a file earlier in the day, check whether you are now reusing an expired resource.
- If the route is clearly correct but the same error remains, inspect base64 integrity, request transformation in wrappers, or stale client code next.
The important boundary here is what not to blame too early. This symptom usually does not mean Nano Banana Pro suddenly stopped understanding images. It usually means the image never reached the model on a supported route. Only after the route is clearly correct should you move into payload corruption, resource expiry, or platform-specific behavior.
If you get past route repair and discover the real problem is elsewhere, the best adjacent follow-up is usually not another unsupported-URI search. It is a broader Gemini image-failure guide. Our Gemini image common errors guide is the right companion when the route is already fixed but the request still breaks for quota, endpoint, parameter, or silent-generation reasons.
FAQ
Can I use a public HTTPS URL directly in native Gemini file_data?
Not as a general rule. A public object URL is not the same thing as a Gemini File resource. On native Gemini, upload the file first or use files.register when your source is a supported GCS object.
Does data:image/...;base64,... belong anywhere in Gemini?
Yes. As of April 9, 2026, the current Gemini OpenAI compatibility docs still support image inputs through image_url, including base64 data: URLs. If you still get the unsupported-file-URI error there, check payload integrity and wrapper behavior before concluding the route itself is unsupported.
Can I pass a local file path such as /tmp/a.png or file:///...?
Not as if it were already a reusable Gemini file URI. A local path is a device-side reference. The safe cross-platform fix is to upload first and reuse the returned file resource.
Does files.register replace upload?
It does not replace every upload workflow. It gives you a current official Gemini route for registering supported GCS objects as File resources. If your file is local, upload is still the normal first move.
What if the same route still fails after I correct it?
That is the point where this stops being a pure route problem. Check corrupted base64, expired file resources, or wrappers and SDKs that rewrote your request on the way out.
The Working Rule
The fastest clean fix is not "change the prompt" and not "retry randomly until Gemini accepts it." It is "identify the surface, move the file onto the route that surface actually supports, verify on the same path, and only then debug payload integrity or platform behavior if the error remains."