diff --git a/.forgejo/workflows/test.yml b/.forgejo/workflows/test.yml
index 088ca7c..df5f59c 100644
--- a/.forgejo/workflows/test.yml
+++ b/.forgejo/workflows/test.yml
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: LGPL-3.0-or-later
+# See Notices.txt for copyright information
 on: [push, pull_request]
 
 jobs:
diff --git a/.gitignore b/.gitignore
index ccb5166..0655406 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
+# SPDX-License-Identifier: LGPL-3.0-or-later
+# See Notices.txt for copyright information
 /target
-.vscode
\ No newline at end of file
+.vscode
diff --git a/README.md b/README.md
index 6e14e9f..438550e 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,7 @@
+<!--
+SPDX-License-Identifier: LGPL-3.0-or-later
+See Notices.txt for copyright information
+-->
 # Fayalite
 
 Fayalite is a library for designing digital hardware -- a hardware description language (HDL) embedded in the Rust programming language. Fayalite's semantics are based on [FIRRTL] as interpreted by [LLVM CIRCT](https://circt.llvm.org/docs/Dialects/FIRRTL/FIRRTLAnnotations/).
diff --git a/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs b/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs
index 7f7d626..30cf90f 100644
--- a/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs
+++ b/crates/fayalite-proc-macros-impl/src/hdl_bundle.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use crate::{
     hdl_type_common::{
         common_derives, get_target, ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedField,
diff --git a/crates/fayalite-proc-macros-impl/src/hdl_enum.rs b/crates/fayalite-proc-macros-impl/src/hdl_enum.rs
index d7e5b61..50fb138 100644
--- a/crates/fayalite-proc-macros-impl/src/hdl_enum.rs
+++ b/crates/fayalite-proc-macros-impl/src/hdl_enum.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use crate::{
     hdl_type_common::{
         common_derives, get_target, ItemOptions, MakeHdlTypeExpr, MaybeParsed, ParsedGenerics,
diff --git a/crates/fayalite-proc-macros-impl/src/hdl_type_common.rs b/crates/fayalite-proc-macros-impl/src/hdl_type_common.rs
index e33d0e0..efbe7f3 100644
--- a/crates/fayalite-proc-macros-impl/src/hdl_type_common.rs
+++ b/crates/fayalite-proc-macros-impl/src/hdl_type_common.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use crate::{fold::impl_fold, kw, Errors, HdlAttr, PairsIterExt};
 use proc_macro2::{Span, TokenStream};
 use quote::{format_ident, quote_spanned, ToTokens};
diff --git a/crates/fayalite/examples/blinky.rs b/crates/fayalite/examples/blinky.rs
index 588ca9a..94c7910 100644
--- a/crates/fayalite/examples/blinky.rs
+++ b/crates/fayalite/examples/blinky.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use clap::Parser;
 use fayalite::{cli, prelude::*};
 
diff --git a/crates/fayalite/src/_docs.rs b/crates/fayalite/src/_docs.rs
index 4d254a7..5b1888b 100644
--- a/crates/fayalite/src/_docs.rs
+++ b/crates/fayalite/src/_docs.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 #![doc = include_str!("../README.md")]
 
 //!
diff --git a/crates/fayalite/src/_docs/modules.rs b/crates/fayalite/src/_docs/modules.rs
index c392f2e..99b98e8 100644
--- a/crates/fayalite/src/_docs/modules.rs
+++ b/crates/fayalite/src/_docs/modules.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Fayalite Modules
 //!
 //! The [`#[hdl_module]`][`crate::hdl_module`] attribute is applied to a Rust
diff --git a/crates/fayalite/src/_docs/modules/extern_module.rs b/crates/fayalite/src/_docs/modules/extern_module.rs
index bf2034b..c1367d9 100644
--- a/crates/fayalite/src/_docs/modules/extern_module.rs
+++ b/crates/fayalite/src/_docs/modules/extern_module.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! These are for when you want to use modules written in
 //! some other language, such as Verilog.
 //!
diff --git a/crates/fayalite/src/_docs/modules/module_bodies.rs b/crates/fayalite/src/_docs/modules/module_bodies.rs
index bd85c61..c12ae21 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Module Function Bodies
 //!
 //! The `#[hdl_module]` attribute lets you have statements/expressions with `#[hdl]` annotations
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_array_expressions.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_array_expressions.rs
index c4bbfa4..c0b15ad 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_array_expressions.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_array_expressions.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl]` Array Expressions
 //!
 //! `#[hdl]` can be used on Array Expressions to construct an [`Array<[T; N]>`][type@Array] expression:
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_if_statements.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_if_statements.rs
index 46bb568..7d09943 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_if_statements.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_if_statements.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl] if` Statements
 //!
 //! `#[hdl] if` statements behave similarly to Rust `if` statements, except they end up as muxes
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs
index c4e3e70..61d29b5 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ## `#[hdl] let` statements
 
 pub mod inputs_outputs;
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/inputs_outputs.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/inputs_outputs.rs
index bfd7521..14169d9 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/inputs_outputs.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/inputs_outputs.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Inputs/Outputs
 //!
 //! Inputs/Outputs create a Rust variable with type [`Expr<T>`] where `T` is the type of the input/output.
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/instances.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/instances.rs
index 2776754..75def03 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/instances.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/instances.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Module Instances
 //!
 //! module instances are kinda like the hardware equivalent of calling a function,
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/memories.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/memories.rs
index e491eef..ddd60b9 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/memories.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/memories.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Memories
 //!
 //! Memories are optimized for storing large amounts of data.
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/registers.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/registers.rs
index 28db27f..5a81c5b 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/registers.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/registers.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Registers
 //!
 //! Registers are memory devices that will change their state only on a clock
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/wires.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/wires.rs
index b22e0fd..7d92b41 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/wires.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_let_statements/wires.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! ### Wires
 //!
 //! Wires are kinda like variables, but unlike registers,
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_literals.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_literals.rs
index a6c9b58..91710e7 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_literals.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_literals.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `_hdl`-suffixed literals
 //!
 //! You can have integer literals with an arbitrary number of bits like so:
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs
index c0d4ea6..9e6c511 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_match_statements.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl] match` Statements
 //!
 //! `#[hdl] match` statements behave similarly to Rust `match` statements, except they end up as muxes
diff --git a/crates/fayalite/src/_docs/modules/module_bodies/hdl_struct_variant_expressions.rs b/crates/fayalite/src/_docs/modules/module_bodies/hdl_struct_variant_expressions.rs
index 9d63895..68cd685 100644
--- a/crates/fayalite/src/_docs/modules/module_bodies/hdl_struct_variant_expressions.rs
+++ b/crates/fayalite/src/_docs/modules/module_bodies/hdl_struct_variant_expressions.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # `#[hdl]` Struct/Variant Expressions
 //!
 //! Note: Structs are also known as [Bundles] when used in Fayalite, the Bundle name comes from [FIRRTL].
diff --git a/crates/fayalite/src/_docs/modules/normal_module.rs b/crates/fayalite/src/_docs/modules/normal_module.rs
index f84678e..1267551 100644
--- a/crates/fayalite/src/_docs/modules/normal_module.rs
+++ b/crates/fayalite/src/_docs/modules/normal_module.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Normal Modules
 //!
 //! See also: [Extern Modules][`super::extern_module`]
diff --git a/crates/fayalite/src/_docs/semantics.rs b/crates/fayalite/src/_docs/semantics.rs
index a499e8e..2282f25 100644
--- a/crates/fayalite/src/_docs/semantics.rs
+++ b/crates/fayalite/src/_docs/semantics.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Fayalite Semantics
 //!
 //! Fayalite's semantics are based on [FIRRTL]. Due to their significance, some of the semantics are also documented here.
diff --git a/crates/fayalite/src/_docs/semantics/connection_semantics.rs b/crates/fayalite/src/_docs/semantics/connection_semantics.rs
index 41155bf..ba2a679 100644
--- a/crates/fayalite/src/_docs/semantics/connection_semantics.rs
+++ b/crates/fayalite/src/_docs/semantics/connection_semantics.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 //! # Connection Semantics
 //!
 //! Fayalite's connection semantics are unlike assignments in software, so be careful!
diff --git a/crates/fayalite/src/cli.rs b/crates/fayalite/src/cli.rs
index f848d36..5071279 100644
--- a/crates/fayalite/src/cli.rs
+++ b/crates/fayalite/src/cli.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use crate::{
     bundle::{Bundle, BundleType},
     firrtl,
diff --git a/crates/fayalite/src/expr/target.rs b/crates/fayalite/src/expr/target.rs
index f33b286..0f85f62 100644
--- a/crates/fayalite/src/expr/target.rs
+++ b/crates/fayalite/src/expr/target.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use crate::{
     array::Array,
     bundle::{Bundle, BundleField},
diff --git a/crates/fayalite/src/prelude.rs b/crates/fayalite/src/prelude.rs
index bedece2..6a74e67 100644
--- a/crates/fayalite/src/prelude.rs
+++ b/crates/fayalite/src/prelude.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 pub use crate::{
     annotations::Annotation,
     array::{Array, ArrayType},
diff --git a/crates/fayalite/src/util/ready_valid.rs b/crates/fayalite/src/util/ready_valid.rs
index a5893cf..ec761c2 100644
--- a/crates/fayalite/src/util/ready_valid.rs
+++ b/crates/fayalite/src/util/ready_valid.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 use crate::prelude::*;
 
 #[hdl]
diff --git a/crates/fayalite/src/util/scoped_ref.rs b/crates/fayalite/src/util/scoped_ref.rs
index f168853..7705377 100644
--- a/crates/fayalite/src/util/scoped_ref.rs
+++ b/crates/fayalite/src/util/scoped_ref.rs
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
 mod safety_boundary {
     use std::{cell::Cell, ptr::NonNull};
 
diff --git a/crates/fayalite/visit_types.json b/crates/fayalite/visit_types.json
index 1748e47..ad9ed25 100644
--- a/crates/fayalite/visit_types.json
+++ b/crates/fayalite/visit_types.json
@@ -1,4 +1,8 @@
 {
+    "license_header": [
+        "SPDX-License-Identifier: LGPL-3.0-or-later",
+        "See Notices.txt for copyright information"
+    ],
     "types": {
         "Module": {
             "data": {