If you've opened Google Apps Script (GAS) recently, you might have seen this warning for the first time:
"Rhino Deprecation: Apps Script will discontinue support for the Rhino runtime after January 31, 2026…"
This isn't just a warning; it signifies a major update to the GAS execution environment. This article explains the meaning and background in detail.
🦏 What is Rhino? Why did it exist?
Rhino is the "mechanism (execution engine) that runs JavaScript" used by older versions of Google Apps Script.
GAS is written in JavaScript, but the code doesn't run on its own. It needs an "engine" to execute the JavaScript commands.
That old execution engine was Rhino.
Think of it like having a recipe (code) but needing cooking utensils (runtime) to actually cook. Rhino was an engine based on older JavaScript specifications (ECMAScript 5, etc.).
What is a JavaScript Engine?
A JavaScript engine is the "brain" that interprets and executes the JavaScript code you write.
- Parses the code written as strings
- Actually performs actions according to commands
- Handles errors and optimization
In GAS, your script is executed by this engine provided by Google.
🚫 What does "Deprecated" mean?
"Deprecated" is an official declaration that something should no longer be used.
According to Google's official support schedule, Rhino became deprecated as of February 20, 2025.
Being deprecated means:
- It will still work for now
- But it will definitely stop working in the future (cut off by next January)
This is a common term in software platforms. It's like an official notice saying, "You can still cross this bridge, but we're demolishing it next year."
📅 What does "End of Support" mean?
End of Support indicates when it will completely stop working.
Google's official information states:
The Rhino runtime will work until January 31, 2026. After that, it will no longer be executable.
In other words…
Come February 2026, → Scripts based on Rhino will likely fail with errors.
After support ends:
- Errors will occur
- Automatic executions (triggers) will stop
- Integrations with other services will break
🧠 So, what is the V8 Runtime?
V8 is the current standard JavaScript engine for GAS, which is also used in the Google Chrome browser. It is a high-speed, high-functionality execution engine.
Key points of V8:
- Supports modern JavaScript specifications (ES6 and later)
- Supports modern syntax like let, const, async/await
- High speed and stability
- Future feature expansions assume V8
GAS officially strongly recommends migrating from Rhino to V8.
🐢 Why is Rhino ending?
To summarize the background:
- Time has passed since V8 release, and it's effectively the standard.
- Most users are already working with V8.
- Google wants to standardize this.
- Rhino is old and has non-standard behaviors.
- Rhino has specific non-standard behaviors, making it less compatible with modern JavaScript.
- Google wants to reduce maintenance load.
- Consolidating to one runtime makes it easier to improve quality and fix bugs.
📌 When did Google announce this?
Here is the important timeline:
📌 Why did this appear on your GAS?
Seeing this warning means your script is:
✔ Still running with Rhino runtime specified → And the deadline is approaching
Note: Scripts created after 2020 likely default to V8, but older scripts may still be set to Rhino.
🧩 Differences between Rhino and V8 (Official Examples)
Since V8 is standard-compliant, some behaviors differ from Rhino. Official examples include:
- for each … in is no longer available
- Date.prototype.getYear() behavior changes
- Reserved words cannot be used as variable names
- Reassigning const causes an error
And so on.
🏁 Conclusion
- Rhino is an old runtime ending on 2026/1/31.
- V8 is the current standard and the premise for future GAS.
- If you still have Rhino scripts, switch to V8 and test them soon.
We will explain the specific steps to switch in the next article.
👉 How to Switch GAS from Rhino to V8 and Verify the Migration
【Summary Article】 Here is the complete guide summarizing all information about "Rhino Deprecation / V8 Migration" including this article. 👉 Complete Guide to GAS Rhino Deprecation & V8 Migration
