diff --git a/garde/tests/rules/byte_length.rs b/garde/tests/rules/byte_length.rs
index 0257928..139259a 100644
--- a/garde/tests/rules/byte_length.rs
+++ b/garde/tests/rules/byte_length.rs
@@ -1,7 +1,10 @@
 use super::util;
+
+const UWU: usize = 101;
+
 #[derive(Debug, garde::Validate)]
 struct Test<'a> {
-    #[garde(byte_length(min = 10, max = 100))]
+    #[garde(byte_length(min = 10, max = UWU - 1))]
     field: &'a str,
 
     #[garde(inner(length(min = 10, max = 100)))]
diff --git a/garde_derive/src/check.rs b/garde_derive/src/check.rs
index a5d25a5..5fff8fd 100644
--- a/garde_derive/src/check.rs
+++ b/garde_derive/src/check.rs
@@ -5,7 +5,7 @@ use syn::parse_quote;
 use syn::spanned::Spanned;
 
 use crate::model;
-use crate::util::MaybeFoldError;
+use crate::util::{default_ctx_name, MaybeFoldError};
 
 pub fn check(input: model::Input) -> syn::Result<model::Validate> {
     let model::Input {
@@ -25,7 +25,7 @@ pub fn check(input: model::Input) -> syn::Result<model::Validate> {
         Ok(v) => v,
         Err(e) => {
             error.maybe_fold(e);
-            parse_quote!(())
+            (parse_quote!(()), default_ctx_name())
         }
     };
 
@@ -92,7 +92,7 @@ fn check_attrs(attrs: &[(Span, model::Attr)]) -> syn::Result<()> {
     }
 }
 
-fn get_context(attrs: &[(Span, model::Attr)]) -> syn::Result<syn::Type> {
+fn get_context(attrs: &[(Span, model::Attr)]) -> syn::Result<(syn::Type, syn::Ident)> {
     #![allow(clippy::single_match)]
 
     let error = None;
@@ -100,7 +100,7 @@ fn get_context(attrs: &[(Span, model::Attr)]) -> syn::Result<syn::Type> {
 
     for (_, attr) in attrs {
         match attr {
-            model::Attr::Context(ty) => context = Some(ty),
+            model::Attr::Context(ty, ident) => context = Some((ty, ident)),
             _ => {}
         }
     }
@@ -110,8 +110,8 @@ fn get_context(attrs: &[(Span, model::Attr)]) -> syn::Result<syn::Type> {
     }
 
     match context {
-        Some(v) => Ok((**v).clone()),
-        None => Ok(parse_quote!(())),
+        Some((ty, id)) => Ok(((**ty).clone(), (*id).clone())),
+        None => Ok((parse_quote!(()), default_ctx_name())),
     }
 }
 
@@ -122,7 +122,7 @@ fn get_options(attrs: &[(Span, model::Attr)]) -> model::Options {
 
     for (_, attr) in attrs {
         match attr {
-            model::Attr::Context(_) => {}
+            model::Attr::Context(..) => {}
             model::Attr::AllowUnvalidated => options.allow_unvalidated = true,
         }
     }
@@ -307,8 +307,8 @@ fn check_rule(
         IpV6 => apply!(rule_set, IpV6(), span),
         CreditCard => apply!(rule_set, CreditCard(), span),
         PhoneNumber => apply!(rule_set, PhoneNumber(), span),
-        Length(v) => apply!(rule_set, Length(check_range(v)?), span),
-        ByteLength(v) => apply!(rule_set, ByteLength(check_range(v)?), span),
+        Length(v) => apply!(rule_set, Length(check_range_generic(v)?), span),
+        ByteLength(v) => apply!(rule_set, ByteLength(check_range_generic(v)?), span),
         Range(v) => apply!(rule_set, Range(check_range_not_ord(v)?), span),
         Contains(v) => apply!(rule_set, Contains(v), span),
         Prefix(v) => apply!(rule_set, Prefix(v), span),
@@ -339,6 +339,63 @@ trait CheckRange: Sized {
     fn check_range(self) -> syn::Result<model::ValidateRange<Self>>;
 }
 
+fn check_range_generic<L, R>(
+    range: model::Range<model::Either<L, R>>,
+) -> syn::Result<model::ValidateRange<model::Either<L, R>>>
+where
+    L: PartialOrd,
+{
+    macro_rules! map_validate_range {
+        ($value:expr, $wrapper:expr) => {{
+            match $value {
+                model::ValidateRange::GreaterThan(v) => {
+                    model::ValidateRange::GreaterThan($wrapper(v))
+                }
+                model::ValidateRange::LowerThan(v) => model::ValidateRange::LowerThan($wrapper(v)),
+                model::ValidateRange::Between(v1, v2) => {
+                    model::ValidateRange::Between($wrapper(v1), $wrapper(v2))
+                }
+            }
+        }};
+    }
+
+    let range = match (range.span, range.min, range.max) {
+        (span, Some(model::Either::Left(min)), Some(model::Either::Left(max))) => {
+            map_validate_range!(
+                check_range(model::Range {
+                    span,
+                    min: Some(min),
+                    max: Some(max)
+                })?,
+                model::Either::Left
+            )
+        }
+        (span, Some(model::Either::Left(min)), None) => {
+            map_validate_range!(
+                check_range(model::Range {
+                    span,
+                    min: Some(min),
+                    max: None,
+                })?,
+                model::Either::Left
+            )
+        }
+        (span, None, Some(model::Either::Left(max))) => {
+            map_validate_range!(
+                check_range(model::Range {
+                    span,
+                    min: None,
+                    max: Some(max),
+                })?,
+                model::Either::Left
+            )
+        }
+        (span, min, max) => check_range_not_ord(model::Range { span, min, max })?,
+    };
+
+    Ok(range)
+}
+
 fn check_range<T>(range: model::Range<T>) -> syn::Result<model::ValidateRange<T>>
 where
     T: PartialOrd,
diff --git a/garde_derive/src/emit.rs b/garde_derive/src/emit.rs
index 9e9c3e7..36a807e 100644
--- a/garde_derive/src/emit.rs
+++ b/garde_derive/src/emit.rs
@@ -13,7 +13,7 @@ pub fn emit(input: model::Validate) -> TokenStream2 {
 impl ToTokens for model::Validate {
     fn to_tokens(&self, tokens: &mut TokenStream2) {
         let ident = &self.ident;
-        let context_ty = &self.context;
+        let (context_ty, context_ident) = &self.context;
         let (impl_generics, ty_generics, where_clause) = self.generics.split_for_impl();
         let kind = &self.kind;
 
@@ -22,7 +22,9 @@ impl ToTokens for model::Validate {
                 type Context = #context_ty ;
 
                 #[allow(clippy::needless_borrow)]
-                fn validate(&self, __garde_user_ctx: &Self::Context) -> ::core::result::Result<(), ::garde::error::Errors> {
+                fn validate(&self, #context_ident: &Self::Context) -> ::core::result::Result<(), ::garde::error::Errors> {
+                    let __garde_user_ctx = &#context_ident;
+
                     (
                         #kind
                     )
diff --git a/garde_derive/src/model.rs b/garde_derive/src/model.rs
index a637e9f..a26d1cd 100644
--- a/garde_derive/src/model.rs
+++ b/garde_derive/src/model.rs
@@ -12,7 +12,7 @@ pub struct Input {
 
 #[repr(u8)]
 pub enum Attr {
-    Context(Box<Type>),
+    Context(Box<Type>, Ident),
     AllowUnvalidated,
 }
 
@@ -27,7 +27,7 @@ impl Attr {
 
     pub fn name(&self) -> &'static str {
         match self {
-            Attr::Context(_) => "context",
+            Attr::Context(..) => "context",
             Attr::AllowUnvalidated => "allow_unvalidated",
         }
     }
@@ -100,8 +100,8 @@ pub enum RawRuleKind {
     IpV6,
     CreditCard,
     PhoneNumber,
-    Length(Range<usize>),
-    ByteLength(Range<usize>),
+    Length(Range<Either<usize, Expr>>),
+    ByteLength(Range<Either<usize, Expr>>),
     Range(Range<Expr>),
     Contains(Expr),
     Prefix(Expr),
@@ -111,6 +111,24 @@ pub enum RawRuleKind {
     Inner(List<RawRule>),
 }
 
+pub enum Either<L, R> {
+    Left(L),
+    Right(R),
+}
+
+impl<L, R> quote::ToTokens for Either<L, R>
+where
+    L: quote::ToTokens,
+    R: quote::ToTokens,
+{
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        match self {
+            Self::Left(left) => left.to_tokens(tokens),
+            Self::Right(right) => right.to_tokens(tokens),
+        }
+    }
+}
+
 pub enum Pattern {
     Lit(Str),
     Expr(Expr),
@@ -135,7 +153,7 @@ pub struct List<T> {
 pub struct Validate {
     pub ident: Ident,
     pub generics: Generics,
-    pub context: Type,
+    pub context: (Type, Ident),
     pub kind: ValidateKind,
     pub options: Options,
 }
@@ -211,8 +229,8 @@ pub enum ValidateRule {
     IpV6,
     CreditCard,
     PhoneNumber,
-    Length(ValidateRange<usize>),
-    ByteLength(ValidateRange<usize>),
+    Length(ValidateRange<Either<usize, Expr>>),
+    ByteLength(ValidateRange<Either<usize, Expr>>),
     Range(ValidateRange<Expr>),
     Contains(Expr),
     Prefix(Expr),
diff --git a/garde_derive/src/syntax.rs b/garde_derive/src/syntax.rs
index 66ded19..19d9d58 100644
--- a/garde_derive/src/syntax.rs
+++ b/garde_derive/src/syntax.rs
@@ -5,11 +5,12 @@ use syn::ext::IdentExt;
 use syn::parse::Parse;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
+use syn::token::As;
 use syn::{DeriveInput, Token, Type};
 
 use crate::model;
 use crate::model::List;
-use crate::util::MaybeFoldError;
+use crate::util::{default_ctx_name, MaybeFoldError};
 
 pub fn parse(input: DeriveInput) -> syn::Result<model::Input> {
     let mut error = None;
@@ -90,7 +91,13 @@ impl Parse for model::Attr {
                 let content;
                 syn::parenthesized!(content in input);
                 let ty = content.parse::<Type>()?;
-                Ok(model::Attr::Context(Box::new(ty)))
+                let ident = if content.parse::<As>().is_ok() {
+                    content.parse()?
+                } else {
+                    default_ctx_name()
+                };
+
+                Ok(model::Attr::Context(Box::new(ty), ident))
             }
             "allow_unvalidated" => Ok(model::Attr::AllowUnvalidated),
             _ => Err(syn::Error::new(ident.span(), "unrecognized attribute")),
@@ -383,7 +390,11 @@ where
             }
         }
 
-        Ok(model::Range { span, min, max })
+        if let Some(error) = error {
+            Err(error)
+        } else {
+            Ok(model::Range { span, min, max })
+        }
     }
 }
 
@@ -404,6 +415,18 @@ trait FromExpr: Sized {
     fn from_expr(v: syn::Expr) -> syn::Result<Self>;
 }
 
+impl<L, R> FromExpr for model::Either<L, R>
+where
+    L: FromExpr,
+    R: FromExpr,
+{
+    fn from_expr(v: syn::Expr) -> syn::Result<Self> {
+        L::from_expr(v.clone())
+            .map(model::Either::Left)
+            .or_else(|_| R::from_expr(v).map(model::Either::Right))
+    }
+}
+
 impl FromExpr for syn::Expr {
     fn from_expr(v: syn::Expr) -> syn::Result<Self> {
         Ok(v)
diff --git a/garde_derive/src/util.rs b/garde_derive/src/util.rs
index 1868a6d..830db26 100644
--- a/garde_derive/src/util.rs
+++ b/garde_derive/src/util.rs
@@ -12,3 +12,7 @@ impl MaybeFoldError for Option<syn::Error> {
         }
     }
 }
+
+pub fn default_ctx_name() -> syn::Ident {
+    syn::Ident::new("__garde_user_ctx", proc_macro2::Span::call_site())
+}