diff --git a/docs/modules/Decoder.ts.md b/docs/modules/Decoder.ts.md
index 5033359e8..cd173c53a 100644
--- a/docs/modules/Decoder.ts.md
+++ b/docs/modules/Decoder.ts.md
@@ -21,10 +21,6 @@ Added in v2.2.0
 - [UnknownRecord](#unknownrecord)
 - [alt](#alt)
 - [altDecoder](#altdecoder)
-- [alternativeDecoder](#alternativedecoder)
-- [ap](#ap)
-- [applicativeDecoder](#applicativedecoder)
-- [applyDecoder](#applydecoder)
 - [array](#array)
 - [boolean](#boolean)
 - [failure](#failure)
@@ -147,46 +143,6 @@ export declare const altDecoder: Alt1<'io-ts/Decoder'>
 
 Added in v2.2.3
 
-# alternativeDecoder
-
-**Signature**
-
-```ts
-export declare const alternativeDecoder: Alternative1<'io-ts/Decoder'>
-```
-
-Added in v2.2.3
-
-# ap
-
-**Signature**
-
-```ts
-export declare const ap: <A>(fa: Decoder<A>) => <B>(fab: Decoder<(a: A) => B>) => Decoder<B>
-```
-
-Added in v2.2.0
-
-# applicativeDecoder
-
-**Signature**
-
-```ts
-export declare const applicativeDecoder: Applicative1<'io-ts/Decoder'>
-```
-
-Added in v2.2.3
-
-# applyDecoder
-
-**Signature**
-
-```ts
-export declare const applyDecoder: Apply1<'io-ts/Decoder'>
-```
-
-Added in v2.2.3
-
 # array
 
 **Signature**
diff --git a/src/Decoder.ts b/src/Decoder.ts
index 1d8f0373c..a2da8727b 100644
--- a/src/Decoder.ts
+++ b/src/Decoder.ts
@@ -1,9 +1,7 @@
 /**
  * @since 2.2.0
  */
-import { Alternative1 } from 'fp-ts/lib/Alternative'
-import { Applicative1 } from 'fp-ts/lib/Applicative'
-import { Either, either, isLeft, isRight, left, mapLeft, right } from 'fp-ts/lib/Either'
+import { Either, isLeft, isRight, left, mapLeft, right } from 'fp-ts/lib/Either'
 import { NonEmptyArray } from 'fp-ts/lib/NonEmptyArray'
 import { pipe } from 'fp-ts/lib/pipeable'
 import { Forest, Tree } from 'fp-ts/lib/Tree'
@@ -11,7 +9,6 @@ import * as G from './Guard'
 import { Literal, memoize, Schemable1, WithRefinement1, WithUnion1, WithUnknownContainers1 } from './Schemable'
 import { Functor1 } from 'fp-ts/lib/Functor'
 import { Alt1 } from 'fp-ts/lib/Alt'
-import { Apply1 } from 'fp-ts/lib/Apply'
 
 // -------------------------------------------------------------------------------------
 // model
@@ -34,6 +31,10 @@ export interface Decoder<A> {
  */
 export type TypeOf<D> = D extends Decoder<infer A> ? A : never
 
+// -------------------------------------------------------------------------------------
+// DecodeError
+// -------------------------------------------------------------------------------------
+
 const empty: Array<never> = []
 
 /**
@@ -463,28 +464,25 @@ export function union<A extends ReadonlyArray<unknown>>(
 /**
  * @since 2.2.0
  */
-export const alt: <A>(that: () => Decoder<A>) => (fa: Decoder<A>) => Decoder<A> = (that) => (fa) => alt_(fa, that)
-
-const alt_: <A>(fx: Decoder<A>, fy: () => Decoder<A>) => Decoder<A> = (fx, fy) => ({
-  decode: (u) => either.alt(fx.decode(u), () => fy().decode(u))
-})
-
-/**
- * @since 2.2.0
- */
-export const ap: <A>(fa: Decoder<A>) => <B>(fab: Decoder<(a: A) => B>) => Decoder<B> = (fa) => (fab) => ap_(fab, fa)
+export const map: <A, B>(f: (a: A) => B) => (fa: Decoder<A>) => Decoder<B> = (f) => (fa) => map_(fa, f)
 
-const ap_: <A, B>(fab: Decoder<(a: A) => B>, fa: Decoder<A>) => Decoder<B> = (fab, fa) => ({
-  decode: (u) => either.ap(fab.decode(u), fa.decode(u))
+const map_: <A, B>(fa: Decoder<A>, f: (a: A) => B) => Decoder<B> = (fa, f) => ({
+  decode: (u) => {
+    const e = fa.decode(u)
+    return isLeft(e) ? e : right(f(e.right))
+  }
 })
 
 /**
  * @since 2.2.0
  */
-export const map: <A, B>(f: (a: A) => B) => (fa: Decoder<A>) => Decoder<B> = (f) => (fa) => map_(fa, f)
+export const alt: <A>(that: () => Decoder<A>) => (fa: Decoder<A>) => Decoder<A> = (that) => (fa) => alt_(fa, that)
 
-const map_: <A, B>(fa: Decoder<A>, f: (a: A) => B) => Decoder<B> = (fa, f) => ({
-  decode: (u) => either.map(fa.decode(u), f)
+const alt_: <A>(fx: Decoder<A>, fy: () => Decoder<A>) => Decoder<A> = (fx, fy) => ({
+  decode: (u) => {
+    const e = fx.decode(u)
+    return isLeft(e) ? fy().decode(u) : e
+  }
 })
 
 // -------------------------------------------------------------------------------------
@@ -515,25 +513,6 @@ export const functorDecoder: Functor1<URI> = {
   map: map_
 }
 
-/**
- * @since 2.2.3
- */
-export const applyDecoder: Apply1<URI> = {
-  URI,
-  map: map_,
-  ap: ap_
-}
-
-/**
- * @since 2.2.3
- */
-export const applicativeDecoder: Applicative1<URI> = {
-  URI,
-  map: map_,
-  of,
-  ap: ap_
-}
-
 /**
  * @since 2.2.3
  */
@@ -543,18 +522,6 @@ export const altDecoder: Alt1<URI> = {
   alt: alt_
 }
 
-/**
- * @since 2.2.3
- */
-export const alternativeDecoder: Alternative1<URI> = {
-  URI,
-  map: map_,
-  of,
-  ap: ap_,
-  alt: alt_,
-  zero: () => never
-}
-
 /**
  * @since 2.2.3
  */
diff --git a/test/Codec.ts b/test/Codec.ts
index a23635245..c9c30e14e 100644
--- a/test/Codec.ts
+++ b/test/Codec.ts
@@ -31,7 +31,7 @@ const undefinedGuard: G.Guard<undefined> = {
 const undef: C.Codec<undefined, undefined> = C.fromDecoder(D.fromGuard(undefinedGuard, 'undefined'))
 
 describe('Codec', () => {
-  describe('codec', () => {
+  describe('invariantCodec', () => {
     it('imap', () => {
       const codec = C.invariantCodec.imap(
         C.string,
diff --git a/test/Decoder.ts b/test/Decoder.ts
index 28080fac7..80ed42c95 100644
--- a/test/Decoder.ts
+++ b/test/Decoder.ts
@@ -4,27 +4,23 @@ import { pipe } from 'fp-ts/lib/pipeable'
 import * as D from '../src/Decoder'
 
 describe('Decoder', () => {
-  describe('decoder', () => {
+  it('of', () => {
+    const decoder = D.of(1)
+    assert.deepStrictEqual(decoder.decode('aaa'), E.right(1))
+  })
+
+  describe('functorDecoder', () => {
     it('map', () => {
       const decoder = pipe(
         D.string,
         D.map((s) => s.length)
       )
+      assert.deepStrictEqual(decoder.decode(null), E.left([D.tree('cannot decode null, should be string')]))
       assert.deepStrictEqual(decoder.decode('aaa'), E.right(3))
     })
+  })
 
-    it('of', () => {
-      const decoder = D.applicativeDecoder.of(1)
-      assert.deepStrictEqual(decoder.decode(1), E.right(1))
-      assert.deepStrictEqual(decoder.decode('a'), E.right(1))
-    })
-
-    it('ap', () => {
-      const fab = D.applicativeDecoder.of((s: string): number => s.length)
-      const fa = D.string
-      assert.deepStrictEqual(pipe(fab, D.ap(fa)).decode('aaa'), E.right(3))
-    })
-
+  describe('altDecoder', () => {
     it('alt', () => {
       const decoder = pipe(
         D.string,
@@ -33,11 +29,6 @@ describe('Decoder', () => {
       assert.deepStrictEqual(decoder.decode('a'), E.right('a'))
       assert.deepStrictEqual(decoder.decode(1), E.right('1'))
     })
-
-    it('zero', () => {
-      const decoder = D.alternativeDecoder.zero()
-      assert.deepStrictEqual(decoder.decode(null), E.left([D.tree('cannot decode null, should be never')]))
-    })
   })
 
   describe('union', () => {
diff --git a/test/JsonEncoder.ts b/test/JsonEncoder.ts
index 9228f9afc..044f1de91 100644
--- a/test/JsonEncoder.ts
+++ b/test/JsonEncoder.ts
@@ -2,7 +2,7 @@ import * as assert from 'assert'
 import * as JE from '../src/JsonEncoder'
 
 describe('Encoder', () => {
-  describe('JsonEncoder', () => {
+  describe('contravariantJsonEncoder', () => {
     it('contramap', () => {
       const encoder = JE.contravariantJsonEncoder.contramap(JE.schemableJsonEncoder.number, (s: string) => s.length)
       assert.deepStrictEqual(encoder.encode('aaa'), 3)