diff --git a/packages/app/src/providers/h5grove/__snapshots__/h5grove-api.test.ts.snap b/packages/app/src/providers/h5grove/__snapshots__/h5grove-api.test.ts.snap
index fe0a7958e..8c7ec5987 100644
--- a/packages/app/src/providers/h5grove/__snapshots__/h5grove-api.test.ts.snap
+++ b/packages/app/src/providers/h5grove/__snapshots__/h5grove-api.test.ts.snap
@@ -1720,8 +1720,8 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 0,
-        "B": 1,
+        "0": "A",
+        "1": "B",
       },
     },
     "value": 1,
@@ -1753,8 +1753,8 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 256,
-        "B": 257,
+        "256": "A",
+        "257": "B",
       },
     },
     "value": 256,
@@ -1789,9 +1789,9 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 0,
-        "B": 1,
-        "C": 2,
+        "0": "A",
+        "1": "B",
+        "2": "C",
       },
     },
     "value": Uint8Array [
@@ -1838,9 +1838,9 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 0,
-        "B": 1,
-        "C": 2,
+        "0": "A",
+        "1": "B",
+        "2": "C",
       },
     },
     "value": Uint8Array [
diff --git a/packages/app/src/providers/hsds/utils.ts b/packages/app/src/providers/hsds/utils.ts
index 6379994df..cc1fce295 100644
--- a/packages/app/src/providers/hsds/utils.ts
+++ b/packages/app/src/providers/hsds/utils.ts
@@ -17,13 +17,11 @@ import type {
 } from '@h5web/shared/hdf5-models';
 import { DTypeClass } from '@h5web/shared/hdf5-models';
 import {
-  boolType,
   compoundType,
   cplxType,
-  enumType,
+  enumOrBoolType,
   floatType,
   intType,
-  isBoolEnumType,
   strType,
   uintType,
   unknownType,
@@ -123,9 +121,7 @@ function convertHsdsCompoundType(
 function convertHsdsEnumType(hsdsType: HsdsEnumType): EnumType | BooleanType {
   const { base, mapping } = hsdsType;
   assertHsdsNumericType(base);
-
-  const type = enumType(convertHsdsNumericType(base), mapping);
-  return isBoolEnumType(type) ? boolType() : type; // booleans stored as enums by h5py
+  return enumOrBoolType(convertHsdsNumericType(base), mapping);
 }
 
 export function convertHsdsType(hsdsType: HsdsType): DType {
diff --git a/packages/h5wasm/src/__snapshots__/h5wasm-api.test.ts.snap b/packages/h5wasm/src/__snapshots__/h5wasm-api.test.ts.snap
index c96a289e0..9939b822f 100644
--- a/packages/h5wasm/src/__snapshots__/h5wasm-api.test.ts.snap
+++ b/packages/h5wasm/src/__snapshots__/h5wasm-api.test.ts.snap
@@ -1966,8 +1966,8 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 0,
-        "B": 1,
+        "0": "A",
+        "1": "B",
       },
     },
     "value": 1,
@@ -1999,8 +1999,8 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 256,
-        "B": 257,
+        "256": "A",
+        "257": "B",
       },
     },
     "value": 256,
@@ -2035,9 +2035,9 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 0,
-        "B": 1,
-        "C": 2,
+        "0": "A",
+        "1": "B",
+        "2": "C",
       },
     },
     "value": Uint8Array [
@@ -2084,9 +2084,9 @@ exports[`test file matches snapshot 1`] = `
       },
       "class": "Enumeration",
       "mapping": {
-        "A": 0,
-        "B": 1,
-        "C": 2,
+        "0": "A",
+        "1": "B",
+        "2": "C",
       },
     },
     "value": Uint8Array [
diff --git a/packages/shared/src/hdf5-models.ts b/packages/shared/src/hdf5-models.ts
index 8c5b20b72..4e18a3c99 100644
--- a/packages/shared/src/hdf5-models.ts
+++ b/packages/shared/src/hdf5-models.ts
@@ -175,7 +175,7 @@ export interface ArrayType<T extends DType = DType> {
 export interface EnumType {
   class: DTypeClass.Enum;
   base: NumericType; // technically, only int/uint
-  mapping: Record<string, number>;
+  mapping: Record<number, string>;
 }
 
 export interface TimeType {
diff --git a/packages/shared/src/hdf5-utils.ts b/packages/shared/src/hdf5-utils.ts
index b62638485..d4dae41ae 100644
--- a/packages/shared/src/hdf5-utils.ts
+++ b/packages/shared/src/hdf5-utils.ts
@@ -143,29 +143,31 @@ export function arrayType<T extends DType>(
 
 export function enumType(
   baseType: NumericType,
-  mapping: Record<string, number>,
+  hdf5Mapping: Record<string, number>,
 ): EnumType {
-  return { class: DTypeClass.Enum, base: baseType, mapping };
-}
-
-export function isBoolEnumType(type: EnumType): boolean {
-  const { mapping } = type;
-  return (
-    Object.keys(mapping).length === 2 &&
-    mapping.FALSE === 0 &&
-    mapping.TRUE === 1
-  );
+  return {
+    class: DTypeClass.Enum,
+    base: baseType,
+    // Swap mapping to optimise retrieval of enum keys from numeric values
+    mapping: Object.fromEntries(
+      Object.entries(hdf5Mapping).map(([k, v]) => [v, k]),
+    ),
+  };
 }
 
 export function enumOrBoolType(
   baseType: NumericType,
-  mapping: Record<string, number>,
+  hdf5Mapping: Record<string, number>,
 ): EnumType | BooleanType {
-  if (mapping.FALSE === 0 && mapping.TRUE === 1) {
+  if (
+    Object.keys(hdf5Mapping).length === 2 &&
+    hdf5Mapping.FALSE === 0 &&
+    hdf5Mapping.TRUE === 1
+  ) {
     return boolType();
   }
 
-  return enumType(baseType, mapping);
+  return enumType(baseType, hdf5Mapping);
 }
 
 export function timeType(): TimeType {
diff --git a/packages/shared/src/vis-utils.ts b/packages/shared/src/vis-utils.ts
index 9cf509304..574be11b4 100644
--- a/packages/shared/src/vis-utils.ts
+++ b/packages/shared/src/vis-utils.ts
@@ -77,12 +77,9 @@ export function createComplexFormatter(
 }
 
 export function createEnumFormatter(
-  mapping: Record<string, number>,
+  mapping: Record<number, string>,
 ): ValueFormatter<EnumType> {
-  return (value) => {
-    const entry = Object.entries(mapping).find(([, v]) => value === v);
-    return entry?.[0] || value.toString();
-  };
+  return (value) => (value in mapping ? mapping[value] : value.toString());
 }
 
 export function getValues(arr: AnyNumArray): NumArray {