Why is my Lambda runtime version different from my Lambda runtime identifier?

Short description

A Lambda function runs with a specific runtime, such as Python 3.14 or Node.js 24.x. Lambda function owners update Lambda runtimes as necessary. Lambda updates each managed runtime with all current security updates, bug fixes, new features, performance enhancements, and support for minor version releases. Then, Lambda publishes these updates as runtime versions. Lambda also applies these runtime updates to Lambda functions that use an earlier runtime version so that they use the new runtime version.

Resolution

Lambda runtime identifiers compared to Lambda runtime versions

Lambda runtime identifiers are different than Lambda runtime versions. The runtime identifier specifies a distinct major release of the programming language, such as nodejs22.x, nodejs24.x, python3.13, or python3.14. The runtime version refers to minor runtime and security patches for your function's launch environment. The runtime version describes the patch version of an individual runtime. For more information, see Introducing AWS Lambda runtime management controls.

Lambda runtime minor versions

Lambda runtime minor versions are different than Lambda runtime versions. To find the runtime version Amazon Resource Name (ARN), complete the following steps:

1. Open the Lambda console.
2. Select your function name.
3. In the Runtime settings section, expand Runtime management configuration and copy the ARN.
   -or-
   Find the runtime version ARN in your Lambda function logs.

The following log appears every time that Lambda creates a new launch environment for your function.

INIT_START Runtime Version: python:3.14.v14    Runtime Version ARN: arn:aws:lambda:eu-south-1::runtime:7b620fc2e66107a1046b140b9d320295811af3ad5d4c6a011fad1fa65127e9e6I

To find the runtime minor version for Node.js-based Lambda functions, log the version with process.version property:

console.log('NODE_VERSION', process.version)

To find the runtime minor version for Python-based Lambda functions, log the version with sys.version property:

import sys
print (sys.version)

Example Python output:

3.12: 3.12.5 (main, Sep 9 2024, 14:55:57) [GCC 11.4.1 20230605 (Red Hat 11.4.1-2)]

Related information

How do I troubleshoot Lambda function failures caused by runtime version errors?

Runtime update modes