Create a context cache

You must create a context cache before you can use it. The context cache you create contains a large amount of data that you can use in multiple requests to a Gemini model. The cached content is stored in the region where you make the request to create the cache.

Cached content can be any of the MIME types supported by Gemini multimodal models. For example, you can cache a large amount of text, audio, or video. You can specify more than one file to cache. For more information, see the following media requirements:

You specify the content to cache using a blob, text, or a path to a file that's stored in a Cloud Storage bucket. If the size of the content you're caching is greater than 10 MB, then you must specify it using the URI of a file that's stored in a Cloud Storage bucket.

Cached content has a finite lifespan. The default expiration time of a context cache is 60 minutes after it's created. If you want a different expiration time, you can specify a different expiration time using the ttl or the expire_time property when you create a context cache. You can also update the expiration time for an unexpired context cache. For information about how to specify ttl and expire_time, see Update the expiration time.

After a context cache expires, it's no longer available. If you want to reference the content in an expired context cache in future prompt requests, then you need to recreate the context cache.

Limits

The content that you cache must adhere to the limits shown in the following table:

Context caching limits

Minimum cache token count
  • 2,048 (Gemini 2.5 Pro)
  • 1,024 (Gemini 2.5 Flash)
  • 1,024 (Gemini 2.0 Flash)
  • 1,024 (Gemini 2.0 Flash-Lite)

Maximum size of content you can cache using a blob or text

 10 MB

Minimum time before a cache expires after it's created

 1 minute

Maximum time before a cache expires after it's created

 There isn't a maximum cache duration

Location support

Context caching isn't supported in the Sydney, Australia (australia-southeast1) region.

Encryption key support

Context caching supports Customer-Managed Encryption Keys (CMEKs), allowing you to control the encryption of your cached data and protect your sensitive information with encryption keys that you manage and own. This provides an additional layer of security and compliance.

Refer to the example for more details.

Access Transparency support

Context caching supports Access Transparency.

Create context cache example

The following examples show how to create a context cache.

Python

Install

pip install --upgrade google-genai

To learn more, see the SDK reference documentation.

Set environment variables to use the Gen AI SDK with Vertex AI: 

# Replace the `GOOGLE_CLOUD_PROJECT` and `GOOGLE_CLOUD_LOCATION` values
# with appropriate values for your project.
export GOOGLE_CLOUD_PROJECT=GOOGLE_CLOUD_PROJECT
export GOOGLE_CLOUD_LOCATION=us-central1
export GOOGLE_GENAI_USE_VERTEXAI=True
 

from google import genai
from google.genai.types import Content, CreateCachedContentConfig, HttpOptions, Part

client = genai.Client(http_options=HttpOptions(api_version="v1"))

system_instruction = """
You are an expert researcher. You always stick to the facts in the sources provided, and never make up new facts.
Now look at these research papers, and answer the following questions.
"""

contents = [
    Content(
        role="user",
        parts=[
            Part.from_uri(
                file_uri="gs://cloud-samples-data/generative-ai/pdf/2312.11805v3.pdf",
                mime_type="application/pdf",
            ),
            Part.from_uri(
                file_uri="gs://cloud-samples-data/generative-ai/pdf/2403.05530.pdf",
                mime_type="application/pdf",
            ),
        ],
    )
]

content_cache = client.caches.create(
    model="gemini-2.5-flash",
    config=CreateCachedContentConfig(
        contents=contents,
        system_instruction=system_instruction,
        # (Optional) For enhanced security, the content cache can be encrypted using a Cloud KMS key
        # kms_key_name = "projects/.../locations/us-central1/keyRings/.../cryptoKeys/..."
        display_name="example-cache",
        ttl="86400s",
    ),
)

print(content_cache.name)
print(content_cache.usage_metadata)
# Example response:
#   projects/111111111111/locations/us-central1/cachedContents/1111111111111111111
#   CachedContentUsageMetadata(audio_duration_seconds=None, image_count=167,
#       text_count=153, total_token_count=43130, video_duration_seconds=None)

Go

Learn how to install or update the Go.

To learn more, see the SDK reference documentation.

Set environment variables to use the Gen AI SDK with Vertex AI: 

# Replace the `GOOGLE_CLOUD_PROJECT` and `GOOGLE_CLOUD_LOCATION` values
# with appropriate values for your project.
export GOOGLE_CLOUD_PROJECT=GOOGLE_CLOUD_PROJECT
export GOOGLE_CLOUD_LOCATION=us-central1
export GOOGLE_GENAI_USE_VERTEXAI=True
 

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"time"

	genai "google.golang.org/genai"
)

// createContentCache shows how to create a content cache with an expiration parameter.
func createContentCache(w io.Writer) (string, error) {
	ctx := context.Background()

	client, err := genai.NewClient(ctx, &genai.ClientConfig{
		HTTPOptions: genai.HTTPOptions{APIVersion: "v1"},
	})
	if err != nil {
		return "", fmt.Errorf("failed to create genai client: %w", err)
	}

	modelName := "gemini-2.5-flash"

	systemInstruction := "You are an expert researcher. You always stick to the facts " +
		"in the sources provided, and never make up new facts. " +
		"Now look at these research papers, and answer the following questions."

	cacheContents := []*genai.Content{
		{
			Parts: []*genai.Part{
				{FileData: &genai.FileData{
					FileURI:  "gs://cloud-samples-data/generative-ai/pdf/2312.11805v3.pdf",
					MIMEType: "application/pdf",
				}},
				{FileData: &genai.FileData{
					FileURI:  "gs://cloud-samples-data/generative-ai/pdf/2403.05530.pdf",
					MIMEType: "application/pdf",
				}},
			},
			Role: "user",
		},
	}
	config := &genai.CreateCachedContentConfig{
		Contents: cacheContents,
		SystemInstruction: &genai.Content{
			Parts: []*genai.Part{
				{Text: systemInstruction},
			},
		},
		DisplayName: "example-cache",
		TTL:         time.Duration(time.Duration.Seconds(86400)),
	}

	res, err := client.Caches.Create(ctx, modelName, config)
	if err != nil {
		return "", fmt.Errorf("failed to create content cache: %w", err)
	}

	cachedContent, err := json.MarshalIndent(res, "", "  ")
	if err != nil {
		return "", fmt.Errorf("failed to marshal cache info: %w", err)
	}

	// See the documentation: https://pkg.go.dev/google.golang.org/genai#CachedContent
	fmt.Fprintln(w, string(cachedContent))

	// Example response:
	// {
	//   "name": "projects/111111111111/locations/us-central1/cachedContents/1111111111111111111",
	//   "displayName": "example-cache",
	//   "model": "projects/111111111111/locations/us-central1/publishers/google/models/gemini-2.5-flash",
	//   "createTime": "2025-02-18T15:05:08.29468Z",
	//   "updateTime": "2025-02-18T15:05:08.29468Z",
	//   "expireTime": "2025-02-19T15:05:08.280828Z",
	//   "usageMetadata": {
	//     "imageCount": 167,
	//     "textCount": 153,
	//     "totalTokenCount": 43125
	//   }
	// }

	return res.Name, nil
}

REST

You can use REST to create a context cache by using the Vertex AI API to send a POST request to the publisher model endpoint. The following example shows how to create a context cache using a file stored in a Cloud Storage bucket.

Before using any of the request data, make the following replacements:

  • PROJECT_ID: Your project ID.
  • LOCATION: The region to process the request and where the cached content is stored. For a list of supported regions, see Available regions.
  • CACHE_DISPLAY_NAME: A meaningful display name to describe and to help you identify each context cache.
  • MIME_TYPE: The MIME type of the content to cache.
  • CONTENT_TO_CACHE_URI: The Cloud Storage URI of the content to cache.
  • MODEL_ID: The model to use for caching.

HTTP method and URL: 

POST https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/cachedContents

Request JSON body: 

{
  "model": "projects/PROJECT_ID/locations/LOCATION/publishers/google/models/MODEL_ID",
  "displayName": "CACHE_DISPLAY_NAME",
  "contents": [{
    "role": "user",
      "parts": [{
        "fileData": {
          "mimeType": "MIME_TYPE",
          "fileUri": "CONTENT_TO_CACHE_URI"
        }
      }]
  },
  {
    "role": "model",
      "parts": [{
        "text": "This is sample text to demonstrate explicit caching."
      }]
  }]
}

To send your request, choose one of these options:

curl

Save the request body in a file named request.json, and execute the following command: 

curl -X POST \
     -H "Authorization: Bearer $(gcloud auth print-access-token)" \
     -H "Content-Type: application/json; charset=utf-8" \
     -d @request.json \
     "https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/cachedContents"

PowerShell

Save the request body in a file named request.json, and execute the following command: 

$cred = gcloud auth print-access-token
$headers = @{ "Authorization" = "Bearer $cred" }

Invoke-WebRequest `
    -Method POST `
    -Headers $headers `
    -ContentType: "application/json; charset=utf-8" `
    -InFile request.json `
    -Uri "https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/cachedContents" | Select-Object -Expand Content

You should receive a JSON response similar to the following:

Example curl command

LOCATION="us-central1"
MODEL_ID="gemini-2.0-flash-001"
PROJECT_ID="test-project"
MIME_TYPE="video/mp4"
CACHED_CONTENT_URI="gs://path-to-bucket/video-file-name.mp4"

curl -X POST \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
-H "Content-Type: application/json" \
https://${LOCATION}-aiplatform.googleapis.com/v1/projects/${PROJECT_ID}/locations/${LOCATION}/cachedContents -d \
'{
  "model":"projects/${PROJECT_ID}/locations/${LOCATION}/publishers/google/models/${MODEL_ID}",
  "contents": [
    {
      "role": "user",
      "parts": [
        {
          "fileData": {
            "mimeType": "${MIME_TYPE}",
            "fileUri": "${CACHED_CONTENT_URI}"
          }
        }
      ]
    }
  ]
}'

Create a context cache with CMEK

To implement context caching with CMEKs, create a CMEK by following the instructions and make sure the Vertex AI per-product, per-project service account (P4SA) has the necessary Cloud KMS CryptoKey Encrypter/Decrypter permissions on the key. This lets you securely create and manage cached content as well make other calls like {List, Update, Delete, Get} CachedContent(s) without repeatedly specifying a KMS key.

REST

You can use REST to create a context cache by using the Vertex AI API to send a POST request to the publisher model endpoint. The following example shows how to create a context cache using a file stored in a Cloud Storage bucket.

Before using any of the request data, make the following replacements:

  • PROJECT_ID: .
  • LOCATION: The region to process the request and where the cached content is stored. For a list of supported regions, see Available regions.
  • MODEL_ID: gemini-2.0-flash-001.
  • CACHE_DISPLAY_NAME: A meaningful display name to describe and to help you identify each context cache.
  • MIME_TYPE: The MIME type of the content to cache.
  • CACHED_CONTENT_URI: The Cloud Storage URI of the content to cache.
  • KMS_KEY_NAME: The Cloud KMS key name.

HTTP method and URL: 

POST https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/cachedContents

Request JSON body: 

{
  "model": "projects/PROJECT_ID/locations/LOCATION/publishers/google/models/gemini-2.0-flash-001",
  "displayName": "CACHE_DISPLAY_NAME",
  "contents": [{
    "role": "user",
      "parts": [{
        "fileData": {
          "mimeType": "MIME_TYPE",
          "fileUri": "CONTENT_TO_CACHE_URI"
        }
      }]}],
    "encryptionSpec": {
      "kmsKeyName": "KMS_KEY_NAME"
    }
}

To send your request, choose one of these options:

curl

Save the request body in a file named request.json, and execute the following command: 

curl -X POST \
     -H "Authorization: Bearer $(gcloud auth print-access-token)" \
     -H "Content-Type: application/json; charset=utf-8" \
     -d @request.json \
     "https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/cachedContents"

PowerShell

Save the request body in a file named request.json, and execute the following command: 

$cred = gcloud auth print-access-token
$headers = @{ "Authorization" = "Bearer $cred" }

Invoke-WebRequest `
    -Method POST `
    -Headers $headers `
    -ContentType: "application/json; charset=utf-8" `
    -InFile request.json `
    -Uri "https://LOCATION-aiplatform.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/cachedContents" | Select-Object -Expand Content

You should receive a JSON response similar to the following:

Example curl command

LOCATION="us-central1"
MODEL_ID="gemini-2.0-flash-001"
PROJECT_ID="test-project"
MIME_TYPE="video/mp4"
CACHED_CONTENT_URI="gs://path-to-bucket/video-file-name.mp4"
KMS_KEY_NAME="projects/${PROJECT_ID}/locations/{LOCATION}/keyRings/your-key-ring/cryptoKeys/your-key"

curl -X POST \
-H "Authorization: Bearer $(gcloud auth print-access-token)" \
-H "Content-Type: application/json" \
https://${LOCATION}-aiplatform.googleapis.com/v1/projects/${PROJECT_ID}/locations/${LOCATION}/cachedContents -d \
'{

"model": "projects/{PROJECT_ID}}/locations/{LOCATION}/publishers/google/models/{MODEL_ID}",
  "contents" : [
    {
      "role": "user",
      "parts": [
        {
          "file_data": {
            "mime_type":"{MIME_TYPE}",
            "file_uri":"{CACHED_CONTENT_URI}"
          }
        }
      ]
    }
  ],
  "encryption_spec" :
  {
    "kms_key_name":"{KMS_KEY_NAME}"
  }
}'

GenAI SDK for Python

Install

pip install --upgrade google-genai

To learn more, see the SDK reference documentation.

Set environment variables to use the Gen AI SDK with Vertex AI:

# Replace the `GOOGLE_CLOUD_PROJECT` and `GOOGLE_CLOUD_LOCATION` values
# with appropriate values for your project.
export GOOGLE_CLOUD_PROJECT=GOOGLE_CLOUD_PROJECT
export GOOGLE_CLOUD_LOCATION=us-central1
export GOOGLE_GENAI_USE_VERTEXAI=True

import os
from google import genai
from google.genai.types import Content, CreateCachedContentConfig, HttpOptions, Part

os.environ['GOOGLE_CLOUD_PROJECT'] = 'vertexsdk'
os.environ['GOOGLE_CLOUD_LOCATION'] = 'us-central1'
os.environ['GOOGLE_GENAI_USE_VERTEXAI'] = 'True'
  
client = genai.Client(http_options=HttpOptions(api_version="v1"))

system_instruction = """
You are an expert researcher. You always stick to the facts in the sources provided, and never make up new facts.
Now look at these research papers, and answer the following questions.
"""

contents = [
    Content(
        role="user",
        parts=[
            Part.from_uri(
                file_uri="gs://cloud-samples-data/generative-ai/pdf/2312.11805v3.pdf",
                mime_type="application/pdf",
            ),
            Part.from_uri(
                file_uri="gs://cloud-samples-data/generative-ai/pdf/2403.05530.pdf",
                mime_type="application/pdf",
            ),
        ],
    )
]

content_cache = client.caches.create(
    model="gemini-2.0-flash-001",
    config=CreateCachedContentConfig(
        contents=contents,
        system_instruction=system_instruction,
        display_name="example-cache",
        kms_key_name="projects/vertexsdk/locations/us-central1/keyRings/your-project/cryptoKeys/your-key",
        ttl="86400s",
    ),
)

print(content_cache.name)
print(content_cache.usage_metadata)

GenAI SDK for Go

Learn how to install or update the Gen AI SDK for Go.

To learn more, see the SDK reference documentation.

Set environment variables to use the Gen AI SDK with Vertex AI:


import (
    "context"
    "encoding/json"
    "fmt"
    "io"

    genai "google.golang.org/genai"
)

// createContentCache shows how to create a content cache with an expiration parameter.
func createContentCache(w io.Writer) (string, error) {
    ctx := context.Background()

    client, err := genai.NewClient(ctx, &genai.ClientConfig{
        HTTPOptions: genai.HTTPOptions{APIVersion: "v1beta1"},
    })
    if err != nil {
        return "", fmt.Errorf("failed to create genai client: %w", err)
    }

    modelName := "gemini-2.0-flash-001"

    systemInstruction := "You are an expert researcher. You always stick to the facts " +
        "in the sources provided, and never make up new facts. " +
        "Now look at these research papers, and answer the following questions."

    cacheContents := []*genai.Content{
        {
            Parts: []*genai.Part{
                {FileData: &genai.FileData{
                    FileURI:  "gs://cloud-samples-data/generative-ai/pdf/2312.11805v3.pdf",
                    MIMEType: "application/pdf",
                }},
                {FileData: &genai.FileData{
                    FileURI:  "gs://cloud-samples-data/generative-ai/pdf/2403.05530.pdf",
                    MIMEType: "application/pdf",
                }},
            },
            Role: "user",
        },
    }
    config := &genai.CreateCachedContentConfig{
        Contents: cacheContents,
        SystemInstruction: &genai.Content{
            Parts: []*genai.Part{
                {Text: systemInstruction},
            },
        },
        DisplayName: "example-cache",
        KmsKeyName:  "projects/vertexsdk/locations/us-central1/keyRings/your-project/cryptoKeys/your-key",
        TTL:         "86400s",
    }

    res, err := client.Caches.Create(ctx, modelName, config)
    if err != nil {
        return "", fmt.Errorf("failed to create content cache: %w", err)
    }

    cachedContent, err := json.MarshalIndent(res, "", "  ")
    if err != nil {
        return "", fmt.Errorf("failed to marshal cache info: %w", err)
    }

    // See the documentation: https://pkg.go.dev/google.golang.org/genai#CachedContent
    fmt.Fprintln(w, string(cachedContent))

    return res.Name, nil
}

What's next