diff --git a/Project.toml b/Project.toml
index 85e4ca031..48b32f932 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "ChainRulesCore"
 uuid = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
-version = "1.26.1"
+version = "2.0.0"
 
 [deps]
 Compat = "34da2185-b29b-5c13-b0c7-acf172513d20"
diff --git a/docs/Project.toml b/docs/Project.toml
index d7a3da37f..862a1e7dd 100644
--- a/docs/Project.toml
+++ b/docs/Project.toml
@@ -7,7 +7,7 @@ Markdown = "d6f4376e-aef5-505a-96c1-9c027394607a"
 Plots = "91a5bcdd-55d7-5caf-9e0b-520d859cae80"
 
 [compat]
-ChainRulesCore = "1"
+ChainRulesCore = "2"
 Compat = "4"
 DocThemeIndigo = "0.1.3"
 Documenter = "1"
diff --git a/src/tangent_types/abstract_zero.jl b/src/tangent_types/abstract_zero.jl
index c5260489e..ba0dffa9b 100644
--- a/src/tangent_types/abstract_zero.jl
+++ b/src/tangent_types/abstract_zero.jl
@@ -17,7 +17,6 @@ Base.iterate(x::AbstractZero) = (x, nothing)
 Base.iterate(::AbstractZero, ::Any) = nothing
 
 Base.first(x::AbstractZero) = x
-Base.tail(x::AbstractZero) = x
 Base.last(x::AbstractZero) = x
 
 Base.Broadcast.broadcastable(x::AbstractZero) = Ref(x)
diff --git a/src/tangent_types/structural_tangent.jl b/src/tangent_types/structural_tangent.jl
index 05d90144d..1cf8695ed 100644
--- a/src/tangent_types/structural_tangent.jl
+++ b/src/tangent_types/structural_tangent.jl
@@ -360,16 +360,6 @@ Base.iszero(::Tangent{<:,Tuple{}}) = true
 Base.first(tangent::Tangent{P,T}) where {P,T<:Union{Tuple,NamedTuple}} = first(backing(canonicalize(tangent)))
 Base.last(tangent::Tangent{P,T}) where {P,T<:Union{Tuple,NamedTuple}} = last(backing(canonicalize(tangent)))
 
-Base.tail(t::Tangent{P}) where {P<:Tuple} = Tangent{_tailtype(P)}(Base.tail(backing(canonicalize(t)))...)
-@generated _tailtype(::Type{P}) where {P<:Tuple} = Tuple{P.parameters[2:end]...}
-Base.tail(t::Tangent{<:Tuple{Any}}) = NoTangent()
-Base.tail(t::Tangent{<:Tuple{}}) = NoTangent()
-
-Base.tail(t::Tangent{P}) where {P<:NamedTuple} = Tangent{_tailtype(P)}(; Base.tail(backing(canonicalize(t)))...)
-_tailtype(::Type{NamedTuple{S,P}}) where {S,P} = NamedTuple{Base.tail(S), _tailtype(P)}
-Base.tail(t::Tangent{<:NamedTuple{<:Any, <:Tuple{Any}}}) = NoTangent()
-Base.tail(t::Tangent{<:NamedTuple{<:Any, <:Tuple{}}}) = NoTangent()
-
 function Base.getindex(tangent::Tangent{P,T}, idx::Int) where {P,T<:Union{Tuple,NamedTuple}}
     back = backing(canonicalize(tangent))
     return unthunk(getfield(back, idx))
diff --git a/src/tangent_types/thunks.jl b/src/tangent_types/thunks.jl
index 6f23ff782..14f92003c 100644
--- a/src/tangent_types/thunks.jl
+++ b/src/tangent_types/thunks.jl
@@ -30,7 +30,6 @@ end
 
 Base.first(x::AbstractThunk) = first(unthunk(x))
 Base.last(x::AbstractThunk) = last(unthunk(x))
-Base.tail(x::AbstractThunk) = Base.tail(unthunk(x))
 
 Base.:(==)(a::AbstractThunk, b::AbstractThunk) = unthunk(a) == unthunk(b)
 
diff --git a/test/tangent_types/abstract_zero.jl b/test/tangent_types/abstract_zero.jl
index 85a9e1d07..98c50cd1f 100644
--- a/test/tangent_types/abstract_zero.jl
+++ b/test/tangent_types/abstract_zero.jl
@@ -100,7 +100,6 @@
         
         @test first(z) === z
         @test last(z) === z
-        @test Base.tail(z) === z
     end
 
     @testset "NoTangent" begin
diff --git a/test/tangent_types/structural_tangent.jl b/test/tangent_types/structural_tangent.jl
index 0972e1dce..dbf214ed9 100644
--- a/test/tangent_types/structural_tangent.jl
+++ b/test/tangent_types/structural_tangent.jl
@@ -84,15 +84,11 @@ end
             @test getindex(Tangent{Tuple{Float64}}(@thunk 2.0^2), 1) == 4.0
             @test getproperty(Tangent{Tuple{Float64}}(2.0), 1) == 2.0
             @test getproperty(Tangent{Tuple{Float64}}(@thunk 2.0^2), 1) == 4.0
-            @test NoTangent() === @inferred Base.tail(tang1)
-            @test NoTangent() === @inferred Base.tail(Tangent{Tuple{}}())
             
             tang3 = Tangent{Tuple{Float64, String, Vector{Float64}}}(1.0, NoTangent(), @thunk [3.0] .+ 4)
             @test @inferred(first(tang3)) === tang3[1] === 1.0
             @test @inferred(last(tang3)) isa Thunk
             @test unthunk(last(tang3)) == [7.0]
-            @test Tuple(@inferred Base.tail(tang3))[1] === NoTangent()
-            @test Tuple(Base.tail(tang3))[end] isa Thunk
 
             NT = NamedTuple{(:a, :b),Tuple{Float64,Float64}}
             @test getindex(Tangent{NT}(; a=(@thunk 2.0^2)), :a) == 4.0
@@ -109,10 +105,6 @@ end
             @test unthunk(first(Tangent{NT}(; a=(@thunk 2.0^2)))) == 4.0
             @test last(Tangent{NT}(; a=(@thunk 2.0^2))) isa ZeroTangent
             
-            ntang1 = @inferred Base.tail(Tangent{NT}(; b=(@thunk 2.0^2)))
-            @test ntang1 isa Tangent{<:NamedTuple{(:b,)}}
-            @test NoTangent() === @inferred Base.tail(ntang1)
-
             # TODO: uncomment this once https://github.com/JuliaLang/julia/issues/35516
             # if VERSION >= v"1.8-"
             #     @test haskey(Tangent{Tuple{Float64}}(2.0), 1) == true
diff --git a/test/tangent_types/thunks.jl b/test/tangent_types/thunks.jl
index f9c5801fb..a5423c6c5 100644
--- a/test/tangent_types/thunks.jl
+++ b/test/tangent_types/thunks.jl
@@ -17,11 +17,9 @@
         @test nothing === iterate(@thunk ()) == iterate(())
     end
     
-    @testset "first, last, tail" begin
+    @testset "first, last" begin
         @test first(@thunk (1,2,3) .+ 4) === 5
         @test last(@thunk (1,2,3) .+ 4) === 7
-        @test Base.tail(@thunk (1,2,3) .+ 4) === (6, 7)
-        @test Base.tail(@thunk NoTangent() * 5) === NoTangent()
     end
 
     @testset "show" begin