⚠️ Breaking Change
Impact Score: 7/10
Deno v1.2.1 — Release Notes & Engineering Impact
Source available — automated, not human-reviewed
Component: deno · Channel: stable. Automated analysis, not a compatibility certification. How this works.
Analysis updated: 2026-11-01.
Breaking-change evidence from the source
- BREAKING(std/fs): remove readFileStr and writeFileStr (#6848, #6847)
⚡ Executive Summary (TL;DR)
Deno v1.2.1. Source highlight: fix: IPv6 hostname should be compressed (#6772)
Who Does This Impact? (Role-Based Analysis)
💻 Software Engineers & Devs
Check the source notes against the package and APIs you use before upgrading.
📊 Product & Engineering Leads
Use the documented changes to assess relevance to your product; release frequency alone is not a quality measure.
⚙️ DevOps & Security
Verify the target version, runtime requirements and rollback procedure in the official documentation.
⚠️ Breaking Changes & Deprecations (1)
- - BREAKING(std/fs): remove readFileStr and writeFileStr (#6848, #6847)
✨ New Features & Capabilities (2)
- feat(std/encoding): add ascii85 module (#6711)
- feat(std/node): add string_decoder (#6638)
⚡ Performance & Enhancements (1)
- refactor(std/datetime): improve weekOfYear (#6741)
🔧 Bug Fixes & Patches (6)
- fix: IPv6 hostname should be compressed (#6772)
- fix: Ignore polling errors caused by return() in watchFs (#6785)
- fix: Improve URL compatibility (#6807)
- fix: ModuleSpecifier removes relative path parts (#6762)
- fix: Share reqwest client between fetch calls (#6792)
- fix: add icon and metadata to deno.exe on Windows (#6693)
📄 View Raw Release Notes (Original Developer Log)
### 1.2.1 / 2020.07.23
Changes in the CLI:
- fix: IPv6 hostname should be compressed (#6772)
- fix: Ignore polling errors caused by return() in watchFs (#6785)
- fix: Improve URL compatibility (#6807)
- fix: ModuleSpecifier removes relative path parts (#6762)
- fix: Share reqwest client between fetch calls (#6792)
- fix: add icon and metadata to deno.exe on Windows (#6693)
- fix: panic for runtime error in TS compiler (#6758)
- fix: providing empty source code for missing compiled files (#6760)
- refactor: Make OpDispatcher a trait (#6736, #6742)
- refactor: Remove duplicate code and allow filename overwrite for DomFile (#6817, #6830)
- upgrade: Rust 1.45.0 (#6791)
- upgrade: rusty_v8 0.7.0 (#6801)
- upgrade: tokio 0.2.22 (#6838)
Changes in std version 0.62.0:
- BREAKING(std/fs): remove readFileStr and writeFileStr (#6848, #6847)
- feat(std/encoding): add ascii85 module (#6711)
- feat(std/node): add string_decoder (#6638)
- fix(std/encoding/toml): could not parse strings with apostrophes/semicolons (#6781)
- fix(std/testing): assertThrows inheritance (#6623)
- fix(std/wasi): remove number overload from rights in path_open (#6768)
- refactor(std/datetime): improve weekOfYear (#6741)
- refactor(std/path): enrich the types in parse_format_test (#6803)
### Install / Upgrade
**Using Deno:**
```sh
deno upgrade --version 1.2.1
```
**With Shell:**
```sh
curl -fsSL https://deno.land/x/install/install.sh | sh -s v1.2.1
```
**With PowerShell:**
```powershell
$v="1.2.1"; iwr https://deno.land/x/install/install.ps1 -useb | iex
```