diff --git a/internal/portal/src/common/JSONViewer/JSONViewer.scss b/internal/portal/src/common/JSONViewer/JSONViewer.scss
new file mode 100644
index 000000000..5c2273fee
--- /dev/null
+++ b/internal/portal/src/common/JSONViewer/JSONViewer.scss
@@ -0,0 +1,98 @@
+.json-viewer {
+  &__header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+
+    > h3 {
+      margin: 0;
+    }
+  }
+
+  &__actions {
+    display: flex;
+    align-items: center;
+    gap: var(--spacing-2);
+  }
+
+  &__expand-all {
+    background: none;
+    border: none;
+    padding: var(--spacing-1) var(--spacing-2);
+    cursor: pointer;
+    color: var(--colors-foreground-neutral-3);
+    border-radius: var(--radius-s);
+
+    &:hover {
+      color: var(--colors-foreground-neutral-2);
+      background: var(--colors-background-hover);
+    }
+  }
+
+  &__content {
+    background-color: var(--colors-background-neutral-2);
+    padding: var(--spacing-3);
+    border-radius: var(--radius-s);
+    margin-top: var(--spacing-3);
+    overflow-x: auto;
+  }
+
+  &__summary {
+    background: none;
+    border: none;
+    padding: 0;
+    cursor: pointer;
+    font-family: var(--font-family-monospace);
+    font-size: inherit;
+    line-height: 1.6;
+    display: inline;
+
+    &:hover &-count {
+      color: var(--colors-foreground-neutral-2);
+    }
+  }
+
+  &__summary-count {
+    color: var(--colors-foreground-neutral-3);
+  }
+
+  &__entries {
+    padding-left: var(--spacing-5);
+  }
+
+  &__entry {
+    line-height: 1.6;
+  }
+
+  &__key {
+    color: var(--colors-foreground-neutral);
+  }
+
+  &__colon {
+    color: var(--colors-foreground-neutral-3);
+  }
+
+  &__comma {
+    color: var(--colors-foreground-neutral-3);
+  }
+
+  &__bracket {
+    color: var(--colors-foreground-neutral-3);
+  }
+
+  &__string {
+    color: var(--colors-code-string);
+  }
+
+  &__number {
+    color: var(--colors-code-number);
+  }
+
+  &__boolean {
+    color: var(--colors-code-boolean);
+  }
+
+  &__null {
+    color: var(--colors-code-null);
+  }
+}
diff --git a/internal/portal/src/common/JSONViewer/JSONViewer.tsx b/internal/portal/src/common/JSONViewer/JSONViewer.tsx
new file mode 100644
index 000000000..64df551e5
--- /dev/null
+++ b/internal/portal/src/common/JSONViewer/JSONViewer.tsx
@@ -0,0 +1,213 @@
+import { useState, useCallback, useMemo } from "react";
+import { CopyButton } from "../CopyButton/CopyButton";
+
+import "./JSONViewer.scss";
+
+function collectPaths(value: unknown, path: string, out: Set<string>) {
+  if (value === null || typeof value !== "object") return;
+  const entries = Array.isArray(value)
+    ? value.map((v, i) => [String(i), v] as const)
+    : Object.entries(value);
+  if (entries.length === 0) return;
+  out.add(path);
+  for (const [k, v] of entries) {
+    collectPaths(v, `${path}.${k}`, out);
+  }
+}
+
+interface JSONViewerProps {
+  data: unknown;
+  label?: string;
+}
+
+const JSONViewer = ({ data, label }: JSONViewerProps) => {
+  const allPaths = useMemo(() => {
+    const paths = new Set<string>();
+    collectPaths(data, "$", paths);
+    return paths;
+  }, [data]);
+
+  const [expanded, setExpanded] = useState<Set<string>>(() => new Set(allPaths));
+
+  const allExpanded = expanded.size >= allPaths.size;
+
+  const handleToggle = () => {
+    setExpanded(allExpanded ? new Set() : new Set(allPaths));
+  };
+
+  const toggleNode = useCallback((path: string) => {
+    setExpanded((prev) => {
+      const next = new Set(prev);
+      if (next.has(path)) {
+        next.delete(path);
+      } else {
+        next.add(path);
+      }
+      return next;
+    });
+  }, []);
+
+  return (
+    <div className="json-viewer">
+      <div className="json-viewer__header">
+        {label && <h3 className="subtitle-m">{label}</h3>}
+        <div className="json-viewer__actions">
+          <button className="json-viewer__expand-all mono-xs" onClick={handleToggle}>
+            {allExpanded ? "Collapse all" : "Expand all"}
+          </button>
+          <CopyButton value={JSON.stringify(data, null, 2)} />
+        </div>
+      </div>
+      <div className="json-viewer__content mono-s">
+        <JSONNode value={data} path="$" expanded={expanded} toggleNode={toggleNode} />
+      </div>
+    </div>
+  );
+};
+
+interface JSONNodeProps {
+  value: unknown;
+  path: string;
+  expanded: Set<string>;
+  toggleNode: (path: string) => void;
+}
+
+const JSONNode = ({ value, path, expanded, toggleNode }: JSONNodeProps) => {
+  if (value === null) {
+    return <span className="json-viewer__null">null</span>;
+  }
+
+  if (typeof value === "boolean") {
+    return (
+      <span className="json-viewer__boolean">{value ? "true" : "false"}</span>
+    );
+  }
+
+  if (typeof value === "number") {
+    return <span className="json-viewer__number">{value}</span>;
+  }
+
+  if (typeof value === "string") {
+    return <span className="json-viewer__string">"{value}"</span>;
+  }
+
+  if (Array.isArray(value)) {
+    return (
+      <CollapsibleNode
+        kind="array"
+        entries={value.map((item, i) => ({
+          key: String(i),
+          value: item,
+          showKey: false,
+        }))}
+        count={value.length}
+        path={path}
+        expanded={expanded}
+        toggleNode={toggleNode}
+      />
+    );
+  }
+
+  if (typeof value === "object") {
+    const entries = Object.entries(value);
+    return (
+      <CollapsibleNode
+        kind="object"
+        entries={entries.map(([k, v]) => ({ key: k, value: v, showKey: true }))}
+        count={entries.length}
+        path={path}
+        expanded={expanded}
+        toggleNode={toggleNode}
+      />
+    );
+  }
+
+  return <span>{String(value)}</span>;
+};
+
+interface CollapsibleEntry {
+  key: string;
+  value: unknown;
+  showKey: boolean;
+}
+
+interface CollapsibleNodeProps {
+  kind: "object" | "array";
+  entries: CollapsibleEntry[];
+  count: number;
+  path: string;
+  expanded: Set<string>;
+  toggleNode: (path: string) => void;
+}
+
+const CollapsibleNode = ({
+  kind,
+  entries,
+  count,
+  path,
+  expanded,
+  toggleNode,
+}: CollapsibleNodeProps) => {
+  const isExpanded = expanded.has(path);
+  const toggle = useCallback(() => toggleNode(path), [toggleNode, path]);
+
+  const openBracket = kind === "object" ? "{" : "[";
+  const closeBracket = kind === "object" ? "}" : "]";
+
+  if (count === 0) {
+    return (
+      <span className="json-viewer__bracket">
+        {openBracket}{closeBracket}
+      </span>
+    );
+  }
+
+  const itemLabel = `${count} ${count === 1 ? "item" : "items"}`;
+  const arrow = isExpanded ? "\u2191" : "\u2193";
+
+  if (!isExpanded) {
+    return (
+      <button className="json-viewer__summary" onClick={toggle}>
+        <span className="json-viewer__bracket">{openBracket}</span>
+        {" "}
+        <span className="json-viewer__summary-count">{itemLabel} {arrow}</span>
+        {" "}
+        <span className="json-viewer__bracket">{closeBracket}</span>
+      </button>
+    );
+  }
+
+  return (
+    <span className="json-viewer__node">
+      <button className="json-viewer__summary" onClick={toggle}>
+        <span className="json-viewer__bracket">{openBracket}</span>
+        {" "}
+        <span className="json-viewer__summary-count">{itemLabel} {arrow}</span>
+      </button>
+      <div className="json-viewer__entries">
+        {entries.map((entry, i) => (
+          <div key={entry.key} className="json-viewer__entry">
+            {entry.showKey && (
+              <>
+                <span className="json-viewer__key">"{entry.key}"</span>
+                <span className="json-viewer__colon">: </span>
+              </>
+            )}
+            <JSONNode
+              value={entry.value}
+              path={`${path}.${entry.key}`}
+              expanded={expanded}
+              toggleNode={toggleNode}
+            />
+            {i < entries.length - 1 && (
+              <span className="json-viewer__comma">,</span>
+            )}
+          </div>
+        ))}
+      </div>
+      <span className="json-viewer__bracket">{closeBracket}</span>
+    </span>
+  );
+};
+
+export default JSONViewer;
diff --git a/internal/portal/src/scenes/Destination/Destination.tsx b/internal/portal/src/scenes/Destination/Destination.tsx
index 1d3260480..f5e42dd91 100644
--- a/internal/portal/src/scenes/Destination/Destination.tsx
+++ b/internal/portal/src/scenes/Destination/Destination.tsx
@@ -5,6 +5,7 @@ import useSWR from "swr";
 
 import Badge from "../../common/Badge/Badge";
 import { CopyButton } from "../../common/CopyButton/CopyButton";
+import JSONViewer from "../../common/JSONViewer/JSONViewer";
 import { Loading } from "../../common/Icons";
 import CONFIGS from "../../config";
 import { useDestinationType } from "../../destination-types";
@@ -224,10 +225,10 @@ const Destination = () => {
                     destination.filter &&
                     Object.keys(destination.filter).length > 0 && (
                       <div className="filter-container">
-                        <h2 className="title-l">Event Filter</h2>
-                        <pre className="filter-json mono-s">
-                          {JSON.stringify(destination.filter, null, 2)}
-                        </pre>
+                        <JSONViewer
+                          data={destination.filter}
+                          label="Event Filter"
+                        />
                       </div>
                     )}
                   <DestinationMetrics destination={destination} />
diff --git a/internal/portal/src/scenes/Destination/Events/AttemptDetails.tsx b/internal/portal/src/scenes/Destination/Events/AttemptDetails.tsx
index a5147b3f1..9fc4d1890 100644
--- a/internal/portal/src/scenes/Destination/Events/AttemptDetails.tsx
+++ b/internal/portal/src/scenes/Destination/Events/AttemptDetails.tsx
@@ -6,6 +6,7 @@ import { Attempt, EventFull } from "../../../typings/Event";
 import Badge from "../../../common/Badge/Badge";
 import RetryDeliveryButton from "../../../common/RetryDeliveryButton/RetryDeliveryButton";
 import { CopyButton } from "../../../common/CopyButton/CopyButton";
+import JSONViewer from "../../../common/JSONViewer/JSONViewer";
 
 const AttemptDetails = ({
   navigateAttempt,
@@ -15,7 +16,7 @@ const AttemptDetails = ({
   const { attempt_id: attemptId, destination_id: destinationId } = useParams();
 
   const { data: attempt } = useSWR<Attempt>(
-    `destinations/${destinationId}/attempts/${attemptId}?include=event.data,response_data`,
+    `destinations/${destinationId}/attempts/${attemptId}?include[]=event.data&include[]=response_data`,
   );
 
   if (!attempt) {
@@ -119,28 +120,19 @@ const AttemptDetails = ({
 
           {event?.data && (
             <div className="attempt-data__section">
-              <h3 className="subtitle-m">Data</h3>
-              <pre className="mono-s">
-                {JSON.stringify(event.data, null, 2)}
-              </pre>
+              <JSONViewer data={event.data} label="Data" />
             </div>
           )}
 
           {event?.metadata && Object.keys(event.metadata).length > 0 && (
             <div className="attempt-data__section">
-              <h3 className="subtitle-m">Metadata</h3>
-              <pre className="mono-s">
-                {JSON.stringify(event.metadata, null, 2)}
-              </pre>
+              <JSONViewer data={event.metadata} label="Metadata" />
             </div>
           )}
 
           {attempt.response_data && (
             <div className="attempt-data__section">
-              <h3 className="subtitle-m">Response</h3>
-              <pre className="mono-s">
-                {JSON.stringify(attempt.response_data, null, 2)}
-              </pre>
+              <JSONViewer data={attempt.response_data} label="Response" />
             </div>
           )}
         </div>