diff --git a/doc/changelogs/v1.21.md b/doc/changelogs/v1.21.md
new file mode 100644
index 000000000000..7c2685afbb23
--- /dev/null
+++ b/doc/changelogs/v1.21.md
@@ -0,0 +1,387 @@
+# Changelog 1.21
+
+## [1.21.0] (2026-07-16)
+
+Freeze period starts 2026-07-02
+
+[1.21.0]: https://github.com/crystal-lang/crystal/releases/1.21.0
+
+### Breaking changes
+
+#### stdlib
+
+- _(text)_ Disable automatic fallback to legacy `PCRE` ([#16924], thanks @straight-shoota)
+
+[#16924]: https://github.com/crystal-lang/crystal/pull/16924
+
+### Features
+
+#### lang
+
+- _(macros)_ Add `TypeNode#all_methods` that includes the type's ancestor's methods ([#16902], thanks @Blacksmoke16)
+
+[#16902]: https://github.com/crystal-lang/crystal/pull/16902
+
+#### stdlib
+
+- _(cli)_ Align long-only options in OptionParser help ([#16914], thanks @kojix2)
+- _(collection)_ Make `Channel(T)` an `Iterator(T)` ([#16916], thanks @jgaskins)
+- _(crypto)_ Add support for OpenSSL 4.0 ([#16839], thanks @straight-shoota)
+- _(networking)_ **[experimental]** Add `Socket#sendfile` (and `Crystal::EventLoop::Socket#sendfile`) ([#16665], thanks @ysbaddaden)
+- _(networking)_ Add `HTTP::WebSocket#receive` as a synchronous call ([#16689], thanks @jgaskins)
+- _(runtime)_ Add `Crystal::EventLoop::FileDescriptor#pread` ([#17068], thanks @ysbaddaden)
+- _(runtime)_ Add `without_main` flag ([#17074], thanks @kojix2)
+- _(serialization)_ Support nested `root` properties in `JSON::Field` ([#17016], thanks @tcoatswo)
+- _(serialization)_ Add `URI::Params::Field(ignore:)`, `ignore_serialize`, `ignore_deserialize` ([#17029], thanks @trypsynth)
+- _(specs)_ Allow chaining `#should`, `#should_not` expectations ([#17020], thanks @straight-shoota)
+- _(system)_ Expose `Path#kind` ([#16917], thanks @Sija)
+- _(system)_ Add splat overloads for `Process.capture`, `.run` and `.new` ([#16975], thanks @straight-shoota)
+- _(system)_ Add `Process::Status.[]` constructor ([#17003], thanks @straight-shoota)
+- _(text)_ Add `String#present?` ([#16930], thanks @Sija)
+- _(text)_ Add `UUID.v6` and `.v8` generators ([#17010], thanks @trypsynth)
+
+[#16665]: https://github.com/crystal-lang/crystal/pull/16665
+[#16689]: https://github.com/crystal-lang/crystal/pull/16689
+[#16839]: https://github.com/crystal-lang/crystal/pull/16839
+[#16914]: https://github.com/crystal-lang/crystal/pull/16914
+[#16916]: https://github.com/crystal-lang/crystal/pull/16916
+[#16917]: https://github.com/crystal-lang/crystal/pull/16917
+[#16930]: https://github.com/crystal-lang/crystal/pull/16930
+[#16975]: https://github.com/crystal-lang/crystal/pull/16975
+[#17003]: https://github.com/crystal-lang/crystal/pull/17003
+[#17010]: https://github.com/crystal-lang/crystal/pull/17010
+[#17016]: https://github.com/crystal-lang/crystal/pull/17016
+[#17020]: https://github.com/crystal-lang/crystal/pull/17020
+[#17029]: https://github.com/crystal-lang/crystal/pull/17029
+[#17068]: https://github.com/crystal-lang/crystal/pull/17068
+[#17074]: https://github.com/crystal-lang/crystal/pull/17074
+
+#### compiler
+
+- _(cli)_ Classify compiler exit reasons ([#17028], thanks @straight-shoota)
+- _(debugger)_ Improve proc debug metadata ([#16830], thanks @skuznetsov)
+- _(debugger)_ Emit debug metadata for constants and class vars ([#16831], thanks @skuznetsov)
+- _(debugger)_ Improve LLDB collection formatters ([#16832], thanks @skuznetsov)
+- _(parser)_ Add `ASTNode#inspect` ([#16699], thanks @straight-shoota)
+- _(parser)_ Parse `MacroVar` with empty expressions: `%var{}` ([#16772], thanks @straight-shoota)
+- _(parser)_ Add `%W` percent string array literals with interpolation ([#16919], thanks @straight-shoota)
+- _(semantic)_ Split branches on `when Bar, Baz` ([#17072], thanks @straight-shoota)
+
+[#16699]: https://github.com/crystal-lang/crystal/pull/16699
+[#16772]: https://github.com/crystal-lang/crystal/pull/16772
+[#16830]: https://github.com/crystal-lang/crystal/pull/16830
+[#16831]: https://github.com/crystal-lang/crystal/pull/16831
+[#16832]: https://github.com/crystal-lang/crystal/pull/16832
+[#16919]: https://github.com/crystal-lang/crystal/pull/16919
+[#17028]: https://github.com/crystal-lang/crystal/pull/17028
+[#17072]: https://github.com/crystal-lang/crystal/pull/17072
+
+#### tools
+
+- _(docs-generator)_ Improve wording in warning about doc generator without LibXML2 ([#16926], thanks @kojix2)
+
+[#16926]: https://github.com/crystal-lang/crystal/pull/16926
+
+### Bugfixes
+
+#### stdlib
+
+- _(cli)_ Fix summary wrapping condition in OptionParser ([#16915], thanks @kojix2)
+- _(cli)_ Avoid `Process.exec` on Windows and explicitly spawn subprocess ([#17049], thanks @straight-shoota)
+- _(collection)_ Fix `Iterator#compact_map` with `EmptyIterator` ([#16928], thanks @straight-shoota)
+- _(collection)_ Fix `Iterator#compact_map` with non-nilable compactor proc ([#16927], thanks @straight-shoota)
+- _(concurrency)_ Fix swapped atomic orderings in `Sync::MU` fast paths ([#17063], thanks @stevegeek)
+- _(llvm)_ Fix use line 0 for unknown debug location ([#17013], thanks @straight-shoota)
+- _(networking)_ Fix `HTTP::Request.form_params?` to recognize `Content-Type` and `charset` ([#16934], [#16971], thanks @swsch, @straight-shoota)
+- _(networking)_ Fix `HTTP::Client` to retry for connection recovery only ([#16981], thanks @straight-shoota)
+- _(networking)_ Disable transport read-ahead for kTLS sockets ([#17053], thanks @jage)
+- _(runtime)_ `Fiber::ExecutionContext::Monitor` compat with old Crystal releases ([#17007], thanks @ysbaddaden)
+- _(runtime)_ `EventLoop::IoUring#open` musn't set `O_NONBLOCK` when blocking ([#17035], thanks @ysbaddaden)
+- _(runtime)_ underperforming unlock conditions in `Sync::MU` ([#17070], thanks @ysbaddaden)
+- _(runtime)_ `fdlock#try_close?` must release ref after yielding to the block ([#17089], thanks @ysbaddaden)
+- _(serialization)_ memory leak in `XML::Node#each_namespace` ([#17038], thanks @ysbaddaden)
+- _(text)_ Fix `IO::Encoder#write` when operating on long strings ([#16797], thanks @jgaskins)
+
+[#16797]: https://github.com/crystal-lang/crystal/pull/16797
+[#16915]: https://github.com/crystal-lang/crystal/pull/16915
+[#16927]: https://github.com/crystal-lang/crystal/pull/16927
+[#16928]: https://github.com/crystal-lang/crystal/pull/16928
+[#16934]: https://github.com/crystal-lang/crystal/pull/16934
+[#16971]: https://github.com/crystal-lang/crystal/pull/16971
+[#16981]: https://github.com/crystal-lang/crystal/pull/16981
+[#17007]: https://github.com/crystal-lang/crystal/pull/17007
+[#17013]: https://github.com/crystal-lang/crystal/pull/17013
+[#17035]: https://github.com/crystal-lang/crystal/pull/17035
+[#17038]: https://github.com/crystal-lang/crystal/pull/17038
+[#17049]: https://github.com/crystal-lang/crystal/pull/17049
+[#17053]: https://github.com/crystal-lang/crystal/pull/17053
+[#17063]: https://github.com/crystal-lang/crystal/pull/17063
+[#17070]: https://github.com/crystal-lang/crystal/pull/17070
+[#17089]: https://github.com/crystal-lang/crystal/pull/17089
+
+#### compiler
+
+- _(cli)_ cross-compile crashes when combined with emit llvm-bc or obj ([#17060], thanks @ysbaddaden)
+- _(cli)_ Remedy short-flag conflict for `crystal spec -p` ([#17062], thanks @straight-shoota)
+- _(codegen)_ Fix codegen treating distinct lib `type` aliases as the same type ([#16961], thanks @stakach)
+- _(codegen)_ **[regression]** Revert "Fix: cross-compile crashes when combined with emit llvm-bc or obj (#17060)" ([#17080], thanks @straight-shoota)
+- _(interpreter)_ Add interpreter `upcast_distinct` for `Pointer` to `Pointer` ([#16962], thanks @stakach)
+- _(interpreter:repl)_ Fix auto-indentation in the REPL when typing classes. ([#16910], thanks @I3oris)
+- _(interpreter:repl)_ Fix interpreter multidispatch cache collision ([#16958], thanks @stakach)
+- _(parser)_ Fix lexing `MacroVar` syntax in literal ([#16779], thanks @straight-shoota)
+- _(parser)_ Fix short block setter call end location ([#17039], thanks @Sija)
+- _(parser)_ Fix parsing macro var without exps followed by macro expression ([#16879], thanks @straight-shoota)
+- _(parser)_ Fix parse parenthesized expression in block arg assignment ([#16894], thanks @straight-shoota)
+- _(parser)_ Do not merge nested `Expression` and `ExceptionHandler` ([#16852], thanks @straight-shoota)
+- _(parser)_ Fix parser silently ignoring `&(...)`, `&[...]`, `&{...}` in assignment ([#16960], thanks @stakach)
+- _(parser)_ Fix parser allow `/` and `//` immediately after `self`, `nil`, `true`, `false` ([#16942], thanks @stakach)
+- _(semantic)_ Fix freeze type of variable declared with `out` ([#16870], thanks @straight-shoota)
+- _(semantic)_ Fix `lookup_matches_in_type` to reject partial matches ([#16867], thanks @straight-shoota)
+- _(semantic)_ Fix location of double splat named tuple typenode entry locations ([#16889], thanks @Blacksmoke16)
+- _(semantic)_ Fix `sizeof`, `offsetof` as generic type argument in inferred ivar type ([#16811], thanks @kojix2)
+- _(semantic)_ Fix macro argument errors for path receiver calls ([#16923], thanks @kojix2)
+- _(semantic)_ Detect uninitialized ancestor ivars through macro_def initializers ([#16959], thanks @stakach)
+- _(semantic)_ Preserve `nil_if_read?` across while cond filters ([#16963], thanks @stakach)
+- _(semantic)_ Keep wider subclass observer when call owner narrows (#16947) ([#16990], thanks @stakach)
+- _(semantic)_ Symmetric `common_descendent` for two generic class types (#10831) ([#16999], thanks @stakach)
+
+[#16779]: https://github.com/crystal-lang/crystal/pull/16779
+[#16811]: https://github.com/crystal-lang/crystal/pull/16811
+[#16852]: https://github.com/crystal-lang/crystal/pull/16852
+[#16867]: https://github.com/crystal-lang/crystal/pull/16867
+[#16870]: https://github.com/crystal-lang/crystal/pull/16870
+[#16879]: https://github.com/crystal-lang/crystal/pull/16879
+[#16889]: https://github.com/crystal-lang/crystal/pull/16889
+[#16894]: https://github.com/crystal-lang/crystal/pull/16894
+[#16910]: https://github.com/crystal-lang/crystal/pull/16910
+[#16923]: https://github.com/crystal-lang/crystal/pull/16923
+[#16942]: https://github.com/crystal-lang/crystal/pull/16942
+[#16958]: https://github.com/crystal-lang/crystal/pull/16958
+[#16959]: https://github.com/crystal-lang/crystal/pull/16959
+[#16960]: https://github.com/crystal-lang/crystal/pull/16960
+[#16961]: https://github.com/crystal-lang/crystal/pull/16961
+[#16962]: https://github.com/crystal-lang/crystal/pull/16962
+[#16963]: https://github.com/crystal-lang/crystal/pull/16963
+[#16990]: https://github.com/crystal-lang/crystal/pull/16990
+[#16999]: https://github.com/crystal-lang/crystal/pull/16999
+[#17039]: https://github.com/crystal-lang/crystal/pull/17039
+[#17060]: https://github.com/crystal-lang/crystal/pull/17060
+[#17062]: https://github.com/crystal-lang/crystal/pull/17062
+[#17080]: https://github.com/crystal-lang/crystal/pull/17080
+
+#### tools
+
+- _(formatter)_ Fix format empty `then` with trailing comment ([#16878], thanks @straight-shoota)
+- _(formatter)_ Fix formatting whitespace in ternary `if` with trailing comments ([#16880], thanks @straight-shoota)
+- _(formatter)_ Fix formatter on empty string literal continuation ([#16817], thanks @straight-shoota)
+- _(formatter)_ Fix format annotations of splat parameter ([#16987], thanks @straight-shoota)
+- _(formatter)_ Fix formatter strip empty lines in heredoc ([#17034], thanks @straight-shoota)
+
+[#16817]: https://github.com/crystal-lang/crystal/pull/16817
+[#16878]: https://github.com/crystal-lang/crystal/pull/16878
+[#16880]: https://github.com/crystal-lang/crystal/pull/16880
+[#16987]: https://github.com/crystal-lang/crystal/pull/16987
+[#17034]: https://github.com/crystal-lang/crystal/pull/17034
+
+### Chores
+
+#### stdlib
+
+- _(files)_ **[deprecation]** Rename parameter to `writable` in `IO::Memory.new` ([#16858], [#16883], thanks @straight-shoota)
+
+[#16858]: https://github.com/crystal-lang/crystal/pull/16858
+[#16883]: https://github.com/crystal-lang/crystal/pull/16883
+
+### Performance
+
+#### stdlib
+
+- _(collection)_ Preallocate correct size for hash in `Hash.zip` ([#17054], thanks @carlhoerberg)
+
+[#17054]: https://github.com/crystal-lang/crystal/pull/17054
+
+### Refactor
+
+#### stdlib
+
+- _(cli)_ Split error helper for compiler CLI into independent methods ([#16984], thanks @straight-shoota)
+- _(cli)_ Refactor compiler code to raise `CompilerError` instead of `abort` ([#16995], thanks @straight-shoota)
+- _(networking)_ Refactor bubbling exceptions from user code in `HTTP::Client#exec(&)` ([#16969], thanks @straight-shoota)
+- _(runtime)_ Internalize `IO::Evented` into `Crystal::EventLoop::Wasi` ([#17030], thanks @ysbaddaden)
+- _(runtime)_ Fix: thread safety of the libevent event loop ([#17031], thanks @ysbaddaden)
+- _(runtime)_ Drop unused `IO::Evented` and `Crystal::ThreadLocalValue` ([#17032], thanks @ysbaddaden)
+- _(runtime)_ Consolidate `#overlapped_connect` and `#overlapped_accept` into `EventLoop::IOCP` ([#17090], thanks @ysbaddaden)
+- _(system)_ Refactor `Dir::Globber` to a struct with instance methods ([#16899], thanks @straight-shoota)
+- _(system)_ Refactor internal `Process` constructor to receive `Crystal::System::Process` ([#16933], thanks @straight-shoota)
+- _(system)_ dont parse but mmap ELF, Mach-O, PE files and some DWARF sections ([#16939], thanks @ysbaddaden)
+
+[#16899]: https://github.com/crystal-lang/crystal/pull/16899
+[#16933]: https://github.com/crystal-lang/crystal/pull/16933
+[#16939]: https://github.com/crystal-lang/crystal/pull/16939
+[#16969]: https://github.com/crystal-lang/crystal/pull/16969
+[#16984]: https://github.com/crystal-lang/crystal/pull/16984
+[#16995]: https://github.com/crystal-lang/crystal/pull/16995
+[#17030]: https://github.com/crystal-lang/crystal/pull/17030
+[#17031]: https://github.com/crystal-lang/crystal/pull/17031
+[#17032]: https://github.com/crystal-lang/crystal/pull/17032
+[#17090]: https://github.com/crystal-lang/crystal/pull/17090
+
+#### compiler
+
+- Replace backticks with `Process.capture` ([#17012], thanks @straight-shoota)
+- _(codegen)_ Set `optsize` and `minsize` fun attributes for the `-Os` and `-Oz` optimization modes ([#16983], thanks @ysbaddaden)
+- _(parser)_ Parse parens in type grammar into `Union#parens` ([#16744], [#16908], thanks @straight-shoota)
+- _(parser)_ Refactor whitespace branch in `Lexer#next_macro_token` [follow-up #16771] ([#16776], thanks @straight-shoota)
+- _(parser)_ Refactor formatter, remove internal `delimited_pair(advance)` ([#17023], thanks @straight-shoota)
+
+[#16744]: https://github.com/crystal-lang/crystal/pull/16744
+[#16776]: https://github.com/crystal-lang/crystal/pull/16776
+[#16908]: https://github.com/crystal-lang/crystal/pull/16908
+[#16983]: https://github.com/crystal-lang/crystal/pull/16983
+[#17012]: https://github.com/crystal-lang/crystal/pull/17012
+[#17023]: https://github.com/crystal-lang/crystal/pull/17023
+
+#### tools
+
+- _(formatter)_ **[breaking]** Standardize parsing of symbol and string array literals ([#16748], thanks @straight-shoota)
+- _(formatter)_ Drop `format_binary` parameter `alternative` ([#16912], thanks @straight-shoota)
+
+[#16748]: https://github.com/crystal-lang/crystal/pull/16748
+[#16912]: https://github.com/crystal-lang/crystal/pull/16912
+
+#### other
+
+- Fix violations reported by ameba 1.7 ([#17021], thanks @straight-shoota)
+
+[#17021]: https://github.com/crystal-lang/crystal/pull/17021
+
+### Documentation
+
+#### stdlib
+
+- _(macros)_ Improve docs for `::delegate` ([#16854], thanks @straight-shoota)
+- _(text)_ Document null-termination on `String#to_unsafe` ([#16869], thanks @mvanhorn)
+- _(text)_ Document `String` is not inheritable ([#17000], thanks @LaskaIDK)
+
+[#16854]: https://github.com/crystal-lang/crystal/pull/16854
+[#16869]: https://github.com/crystal-lang/crystal/pull/16869
+[#17000]: https://github.com/crystal-lang/crystal/pull/17000
+
+#### other
+
+- Fix typo `writable` in documentation ([#16848], thanks @straight-shoota)
+- Format asciidoc ([#16992], thanks @straight-shoota)
+- rumdl: Fix MD077: Continuation line over-indented ([#17085], thanks @straight-shoota)
+
+[#16848]: https://github.com/crystal-lang/crystal/pull/16848
+[#16992]: https://github.com/crystal-lang/crystal/pull/16992
+[#17085]: https://github.com/crystal-lang/crystal/pull/17085
+
+### Specs
+
+#### stdlib
+
+- _(cli)_ Refactor `run_git` spec helper to use `Process.capture_result?` ([#17079], thanks @straight-shoota)
+- _(collection)_ Add specs for `Iterator.empty` ([#17014], thanks @straight-shoota)
+- _(concurrency)_ Fix: Crystal 1.0.0 is confused by file private types ([#17067], thanks @ysbaddaden)
+- _(networking)_ Extract spec helpers `close_connection` and `client_for` for HTTP client specs ([#16968], thanks @straight-shoota)
+- _(text)_ Add specs for range accessor with open ended exclusive range ([#16849], thanks @straight-shoota)
+
+[#16849]: https://github.com/crystal-lang/crystal/pull/16849
+[#16968]: https://github.com/crystal-lang/crystal/pull/16968
+[#17014]: https://github.com/crystal-lang/crystal/pull/17014
+[#17067]: https://github.com/crystal-lang/crystal/pull/17067
+[#17079]: https://github.com/crystal-lang/crystal/pull/17079
+
+#### compiler
+
+- _(cli)_ Add `compiler-cli` test suite ([#17033], thanks @straight-shoota)
+- _(debugger)_ Fix `lldb-check` expectations in debug tests for compatibility with modern LLDB ([#16860], thanks @straight-shoota)
+
+[#16860]: https://github.com/crystal-lang/crystal/pull/16860
+[#17033]: https://github.com/crystal-lang/crystal/pull/17033
+
+#### other
+
+- Remove unnecessary `not_nil!` in spec suite ([#16865], thanks @straight-shoota)
+- Replace `not_nil!` with `should_not(be_nil)` in spec suite ([#16906], thanks @straight-shoota)
+
+[#16865]: https://github.com/crystal-lang/crystal/pull/16865
+[#16906]: https://github.com/crystal-lang/crystal/pull/16906
+
+### Infrastructure
+
+- Update previous Crystal release 1.20.0 ([#16844], thanks @ysbaddaden)
+- Update previous Crystal release 1.20.1 ([#16901], thanks @straight-shoota)
+- Merge `release/1.19`@`1.19.2` into `master` ([#16905], thanks @straight-shoota)
+- Merge `release/1.20`@`1.20.1` into `master` ([#16900], thanks @straight-shoota)
+- Update `devenv.lock` ([#16819], [#16935], [#17006], [#17075], [#17084], thanks @github-actions, @crysbot)
+- Update changelog script ([#16946], thanks @straight-shoota)
+- Extract `CRYSTAL_BOOTSTRAP_VERSION` in `bin/ci` ([#16966], thanks @straight-shoota)
+- Update previous Crystal release 1.20.2 ([#16954], thanks @straight-shoota)
+- Makefile: Split `install` target into subcomponents ([#16980], thanks @straight-shoota)
+- Update `release-update` script ([#16977], thanks @straight-shoota)
+- Makefile: Build manpages for `install` target ([#16991], thanks @straight-shoota)
+- Apply `shfmt` ([#17015], thanks @straight-shoota)
+- Apply `mbake` formatter for `Makefile` ([#17024], thanks @straight-shoota)
+- infra: devenv input for `git-hooks` follows `nixpkgs` ([#17064], thanks @straight-shoota)
+- Replace `markdownlint` with `rumdl` ([#17069], thanks @straight-shoota)
+- Replace `.markdownlint.yaml` with `rumdl.toml` ([#17078], thanks @straight-shoota)
+- _(ci)_ Fix `-Devloop=io_uring` flag in Linux CI ([#16843], thanks @straight-shoota)
+- _(ci)_ Use PAT from GHA environments for `backport` job ([#16864], thanks @straight-shoota)
+- _(ci)_ Use AWS credentials from GHA environments for `deploy_api_docs` job ([#16863], thanks @straight-shoota)
+- _(ci)_ Update GH Actions ([#16836], [#16944], [#17011], [#17042], thanks @renovate)
+- _(ci)_ Use Crysbot token in `update-devenv` workflow to trigger CI ([#16938], thanks @straight-shoota)
+- _(ci)_ Fix tags for nightly docker images ([#16973], thanks @straight-shoota)
+- _(ci)_ Drop separate `aarch64` workflow ([#16965], thanks @straight-shoota)
+- _(ci)_ Update crate-ci/typos action to v1.46.2 ([#16986], thanks @renovate)
+- _(ci)_ Update `macos-15` runners to `macos-26` ([#17022], thanks @straight-shoota)
+- _(ci)_ Upgrade library dependencies for Windows CI ([#17025], thanks @straight-shoota)
+- _(ci)_ Upgrade windows runners to VS 2026 ([#17043], thanks @straight-shoota)
+- _(ci)_ Upgrade nixpkgs 26.05 in `Lint` workflow ([#17066], thanks @straight-shoota)
+
+[#16819]: https://github.com/crystal-lang/crystal/pull/16819
+[#16836]: https://github.com/crystal-lang/crystal/pull/16836
+[#16843]: https://github.com/crystal-lang/crystal/pull/16843
+[#16844]: https://github.com/crystal-lang/crystal/pull/16844
+[#16863]: https://github.com/crystal-lang/crystal/pull/16863
+[#16864]: https://github.com/crystal-lang/crystal/pull/16864
+[#16900]: https://github.com/crystal-lang/crystal/pull/16900
+[#16901]: https://github.com/crystal-lang/crystal/pull/16901
+[#16905]: https://github.com/crystal-lang/crystal/pull/16905
+[#16935]: https://github.com/crystal-lang/crystal/pull/16935
+[#16938]: https://github.com/crystal-lang/crystal/pull/16938
+[#16944]: https://github.com/crystal-lang/crystal/pull/16944
+[#16946]: https://github.com/crystal-lang/crystal/pull/16946
+[#16954]: https://github.com/crystal-lang/crystal/pull/16954
+[#16965]: https://github.com/crystal-lang/crystal/pull/16965
+[#16966]: https://github.com/crystal-lang/crystal/pull/16966
+[#16973]: https://github.com/crystal-lang/crystal/pull/16973
+[#16977]: https://github.com/crystal-lang/crystal/pull/16977
+[#16980]: https://github.com/crystal-lang/crystal/pull/16980
+[#16986]: https://github.com/crystal-lang/crystal/pull/16986
+[#16991]: https://github.com/crystal-lang/crystal/pull/16991
+[#17006]: https://github.com/crystal-lang/crystal/pull/17006
+[#17011]: https://github.com/crystal-lang/crystal/pull/17011
+[#17015]: https://github.com/crystal-lang/crystal/pull/17015
+[#17022]: https://github.com/crystal-lang/crystal/pull/17022
+[#17024]: https://github.com/crystal-lang/crystal/pull/17024
+[#17025]: https://github.com/crystal-lang/crystal/pull/17025
+[#17042]: https://github.com/crystal-lang/crystal/pull/17042
+[#17043]: https://github.com/crystal-lang/crystal/pull/17043
+[#17064]: https://github.com/crystal-lang/crystal/pull/17064
+[#17066]: https://github.com/crystal-lang/crystal/pull/17066
+[#17069]: https://github.com/crystal-lang/crystal/pull/17069
+[#17075]: https://github.com/crystal-lang/crystal/pull/17075
+[#17078]: https://github.com/crystal-lang/crystal/pull/17078
+[#17084]: https://github.com/crystal-lang/crystal/pull/17084
+
+### other
+
+#### stdlib
+
+- _(cli)_ **[deprecation]** Deprecate `Colorize.on_tty_only!` ([#16859], thanks @straight-shoota)
+- _(system)_ **[deprecation]** Hide platform-specific `Process::Status` constructor ([#16997], thanks @straight-shoota)
+
+[#16859]: https://github.com/crystal-lang/crystal/pull/16859
+[#16997]: https://github.com/crystal-lang/crystal/pull/16997
diff --git a/scripts/github-changelog.cr b/scripts/github-changelog.cr
index 4ddb7bf36f6c..3852ea347903 100755
--- a/scripts/github-changelog.cr
+++ b/scripts/github-changelog.cr
@@ -14,10 +14,13 @@
 #   GITHUB_TOKEN: Access token for the GitHub API (required)
 require "http/client"
 require "json"
+require "colorize"
 
 abort "Missing GITHUB_TOKEN env variable" unless ENV["GITHUB_TOKEN"]?
 api_token = ENV["GITHUB_TOKEN"]
 
+MISSING_TOPICS = Set(PullRequest).new
+
 case ARGV.size
 when 0
   abort "Missing <milestone> argument"
@@ -141,6 +144,10 @@ record PullRequest,
     io << "[#" << number << "]"
   end
 
+  def ==(other : self)
+    number == other.number
+  end
+
   def <=>(other : self)
     sort_tuple <=> other.sort_tuple
   end
@@ -173,7 +180,7 @@ record PullRequest,
 
   def topic
     topics.fetch(0) do
-      STDERR.puts "Missing topic for ##{number}"
+      MISSING_TOPICS.add(self)
       nil
     end
   end
@@ -495,3 +502,11 @@ SECTION_TITLES.each do |id, title|
     end
   end
 end
+
+if MISSING_TOPICS.present?
+  Colorize.enabled = true
+  STDERR.puts "Missing topics:"
+  MISSING_TOPICS.each do |pr|
+    STDERR.puts "\e]8;;https://github.com/crystal-lang/crystal/pull/#{pr.number}\e\\#{pr.title.colorize(:white)} (#{pr.number.to_s.colorize(:light_gray)})\e]8;;\e\\ (#{pr.labels.join(", ")})"
+  end
+end
diff --git a/scripts/update-changelog.sh b/scripts/update-changelog.sh
index f4f4d46b634f..981896a064a3 100755
--- a/scripts/update-changelog.sh
+++ b/scripts/update-changelog.sh
@@ -64,8 +64,6 @@ if [ ! -f "$changelog_path" ]; then
   git add "doc/changelogs/README.md"
 fi
 
-printf '\n' >>"$current_changelog"
-
 if grep --silent -E "^## \[$VERSION\]" "$changelog_path"; then
   echo "Replacing section in $changelog_path"
   sed -i -E "/^## \[$VERSION\]/,/^## /{
diff --git a/shard.yml b/shard.yml
index 60451d4f329a..fc8fd61daacb 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,5 +1,5 @@
 name: crystal
-version: 1.21.0-dev
+version: 1.21.0
 
 authors:
   - Crystal Core Team <crystal@manas.tech>
diff --git a/src/SOURCE_DATE_EPOCH b/src/SOURCE_DATE_EPOCH
new file mode 100644
index 000000000000..25a10868d44e
--- /dev/null
+++ b/src/SOURCE_DATE_EPOCH
@@ -0,0 +1 @@
+1784160000
diff --git a/src/VERSION b/src/VERSION
index c6ba48dc6375..3500250a4b05 100644
--- a/src/VERSION
+++ b/src/VERSION
@@ -1 +1 @@
-1.21.0-dev
+1.21.0