diff --git a/devtools/server/actors/promises.js b/devtools/server/actors/promises.js
index 0d81f984d6b8..02930f18add3 100644
--- a/devtools/server/actors/promises.js
+++ b/devtools/server/actors/promises.js
@@ -65,8 +65,8 @@ var PromisesActor = protocol.ActorClassWithSpec(promisesSpec, {
     this._newPromises = [];
     this._promisesSettled = [];
 
-    this.dbg.findSources().forEach(source => {
-      this.parentActor.sources.createSourceActors(source);
+    this.dbg.findScripts().forEach(s => {
+      this.parentActor.sources.createSourceActors(s.source);
     });
 
     this.dbg.onNewScript = s => {
diff --git a/devtools/server/actors/replay/debugger.js b/devtools/server/actors/replay/debugger.js
index 24ae60fa0988..8018f66460e2 100644
--- a/devtools/server/actors/replay/debugger.js
+++ b/devtools/server/actors/replay/debugger.js
@@ -170,23 +170,11 @@ ReplayDebugger.prototype = {
   /////////////////////////////////////////////////////////
 
   _getSource(id) {
-    const source = this._scriptSources[id];
-    if (source) {
-      return source;
+    if (!this._scriptSources[id]) {
+      const data = this._sendRequest({ type: "getSource", id });
+      this._scriptSources[id] = new ReplayDebuggerScriptSource(this, data);
     }
-    return this._addSource(this._sendRequest({ type: "getSource", id }));
-  },
-
-  _addSource(data) {
-    if (!this._scriptSources[data.id]) {
-      this._scriptSources[data.id] = new ReplayDebuggerScriptSource(this, data);
-    }
-    return this._scriptSources[data.id];
-  },
-
-  findSources() {
-    const data = this._sendRequest({ type: "findSources" });
-    return data.map(source => this._addSource(source));
+    return this._scriptSources[id];
   },
 
   /////////////////////////////////////////////////////////
diff --git a/devtools/server/actors/replay/replay.js b/devtools/server/actors/replay/replay.js
index 4e32440e0642..4f63f57cff80 100644
--- a/devtools/server/actors/replay/replay.js
+++ b/devtools/server/actors/replay/replay.js
@@ -465,22 +465,6 @@ function getScriptData(id) {
   };
 }
 
-function getSourceData(id) {
-  const source = gScriptSources.getObject(id);
-  const introductionScript = gScripts.getId(source.introductionScript);
-  return {
-    id: id,
-    text: source.text,
-    url: source.url,
-    displayURL: source.displayURL,
-    elementAttributeName: source.elementAttributeName,
-    introductionScript,
-    introductionOffset: introductionScript ? source.introductionOffset : undefined,
-    introductionType: source.introductionType,
-    sourceMapURL: source.sourceMapURL,
-  };
-}
-
 function forwardToScript(name) {
   return request => gScripts.getObject(request.id)[name](request.value);
 }
@@ -511,16 +495,20 @@ const gRequestHandlers = {
     return RecordReplayControl.getContent(request.url);
   },
 
-  findSources(request) {
-    const sources = [];
-    gScriptSources.forEach((id) => {
-      sources.push(getSourceData(id));
-    });
-    return sources;
-  },
-
   getSource(request) {
-    return getSourceData(request.id);
+    const source = gScriptSources.getObject(request.id);
+    const introductionScript = gScripts.getId(source.introductionScript);
+    return {
+      id: request.id,
+      text: source.text,
+      url: source.url,
+      displayURL: source.displayURL,
+      elementAttributeName: source.elementAttributeName,
+      introductionScript,
+      introductionOffset: introductionScript ? source.introductionOffset : undefined,
+      introductionType: source.introductionType,
+      sourceMapURL: source.sourceMapURL,
+    };
   },
 
   getObject(request) {
diff --git a/devtools/server/actors/thread.js b/devtools/server/actors/thread.js
index 2c268755df0b..9afe2f721365 100644
--- a/devtools/server/actors/thread.js
+++ b/devtools/server/actors/thread.js
@@ -1111,12 +1111,22 @@ const ThreadActor = ActorClassWithSpec(threadSpec, {
   },
 
   /**
-   * Get the source lists from the debugger.
+   * Get the script and source lists from the debugger.
    */
   _discoverSources: function() {
-    const sources = this.dbg.findSources();
-    return Promise.all(sources.map(source => {
-      return this.sources.createSourceActors(source);
+    // Only get one script per Debugger.Source.
+    const sourcesToScripts = new Map();
+    const scripts = this.dbg.findScripts();
+
+    for (let i = 0, len = scripts.length; i < len; i++) {
+      const s = scripts[i];
+      if (s.source) {
+        sourcesToScripts.set(s.source, s);
+      }
+    }
+
+    return Promise.all([...sourcesToScripts.values()].map(script => {
+      return this.sources.createSourceActors(script.source);
     }));
   },
 
diff --git a/js/src/doc/Debugger/Debugger.md b/js/src/doc/Debugger/Debugger.md
index 6a627d26ad1e..73e73315fd9b 100644
--- a/js/src/doc/Debugger/Debugger.md
+++ b/js/src/doc/Debugger/Debugger.md
@@ -357,10 +357,26 @@ other kinds of objects.
     [visible frame][vf] currently on the calling thread's stack, or `null`
     if there are no visible frames on the stack.
 
-<code>findSources()</code>
-:   Return an array of all [`Debugger.Source`][source] instances of all debuggee
+<code>findSources([<i>query</i>]) <i>(not yet implemented)</i></code>
+:   Return an array of all [`Debugger.Source`][source] instances matching
+    <i>query</i>. Each source appears only once in the array. <i>Query</i>
+    is an object whose properties restrict which sources are returned; a
+    source must meet all the criteria given by <i>query</i> to be returned.
+    If <i>query</i> is omitted, we return all sources of all debuggee
     scripts.
 
+    <i>Query</i> may have the following properties:
+
+    `url`
+    :   The source's `url` property must be equal to this value.
+
+    `global`
+    :   The source must have been evaluated in the scope of the given global
+        object. If this property's value is a [`Debugger.Object`][object] instance
+        belonging to this `Debugger` instance, then its referent is used. If the
+        object is not a global object, then the global in whose scope it was
+        allocated is used.
+
     Note that the result may include sources that can no longer ever be
     used by the debuggee: say, eval code that has finished running, or
     source for unreachable functions. Whether such sources appear can be
diff --git a/js/src/jit-test/tests/debug/Debugger-findSources-01.js b/js/src/jit-test/tests/debug/Debugger-findSources-01.js
deleted file mode 100644
index 4cac711e52dc..000000000000
--- a/js/src/jit-test/tests/debug/Debugger-findSources-01.js
+++ /dev/null
@@ -1,4 +0,0 @@
-// In a debugger with no debuggees, findSources should return no scripts.
-
-const dbg = new Debugger;
-assertEq(dbg.findSources().length, 0);
diff --git a/js/src/jit-test/tests/debug/Debugger-findSources-02.js b/js/src/jit-test/tests/debug/Debugger-findSources-02.js
deleted file mode 100644
index da71bf17b958..000000000000
--- a/js/src/jit-test/tests/debug/Debugger-findSources-02.js
+++ /dev/null
@@ -1,15 +0,0 @@
-// In a debugger with scripts, findSources finds the script source.
-
-const g = newGlobal();
-// Declare a function in order to keep the script source alive across GC.
-g.evaluate(`function fa() {}`, { fileName: "a.js" });
-g.evaluate(`function fb() {}`, { fileName: "b.js" });
-g.evaluate(`function fc() {}`, { fileName: "c.js" });
-
-const dbg = new Debugger();
-const gw = dbg.addDebuggee(g);
-
-const sources = dbg.findSources();
-assertEq(sources.filter(s => s.url == "a.js").length, 1);
-assertEq(sources.filter(s => s.url == "b.js").length, 1);
-assertEq(sources.filter(s => s.url == "c.js").length, 1);
diff --git a/js/src/jit-test/tests/debug/Debugger-findSources-03.js b/js/src/jit-test/tests/debug/Debugger-findSources-03.js
deleted file mode 100644
index 2a8d3cb55bdb..000000000000
--- a/js/src/jit-test/tests/debug/Debugger-findSources-03.js
+++ /dev/null
@@ -1,19 +0,0 @@
-// In a debugger with multiple debuggees, findSources finds script sources across all debuggees.
-
-const g1 = newGlobal();
-const g2 = newGlobal();
-// Declare a function in order to keep the script source alive across GC.
-g1.evaluate(`function fa() {}`, { fileName: "a.js" });
-g1.evaluate(`function fb() {}`, { fileName: "b.js" });
-g2.evaluate(`function fc() {}`, { fileName: "c.js" });
-g2.evaluate(`function fd() {}`, { fileName: "d.js" });
-
-const dbg = new Debugger();
-const g1w = dbg.addDebuggee(g1);
-const g2w = dbg.addDebuggee(g2);
-
-const sources = dbg.findSources();
-assertEq(dbg.findSources().filter(s => s.url == "a.js").length, 1);
-assertEq(dbg.findSources().filter(s => s.url == "b.js").length, 1);
-assertEq(dbg.findSources().filter(s => s.url == "c.js").length, 1);
-assertEq(dbg.findSources().filter(s => s.url == "d.js").length, 1);
diff --git a/js/src/vm/Debugger.cpp b/js/src/vm/Debugger.cpp
index eae8d0349646..c1581c6a67ee 100644
--- a/js/src/vm/Debugger.cpp
+++ b/js/src/vm/Debugger.cpp
@@ -4188,73 +4188,19 @@ Debugger::removeDebuggeeGlobal(FreeOp* fop, GlobalObject* global,
 
 static inline DebuggerSourceReferent GetSourceReferent(JSObject* obj);
 
-class MOZ_STACK_CLASS Debugger::QueryBase
-{
-  protected:
-    QueryBase(JSContext* cx, Debugger* dbg)
-      : cx(cx),
-        debugger(dbg),
-        iterMarker(&cx->runtime()->gc),
-        realms(cx->zone()),
-        oom(false)
-    {}
-
-    // The context in which we should do our work.
-    JSContext* cx;
-
-    // The debugger for which we conduct queries.
-    Debugger* debugger;
-
-    // Require the set of realms to stay fixed while this query is alive.
-    gc::AutoEnterIteration iterMarker;
-
-    using RealmSet = HashSet<Realm*, DefaultHasher<Realm*>, ZoneAllocPolicy>;
-
-    // A script must be in one of these realms to match the query.
-    RealmSet realms;
-
-    // Indicates whether OOM has occurred while matching.
-    bool oom;
-
-    bool addRealm(Realm* realm) {
-        return realms.put(realm);
-    }
-
-    // Arrange for this query to match only scripts that run in |global|.
-    bool matchSingleGlobal(GlobalObject* global) {
-        MOZ_ASSERT(realms.count() == 0);
-        if (!addRealm(global->realm())) {
-            ReportOutOfMemory(cx);
-            return false;
-        }
-        return true;
-    }
-
-    // Arrange for this ScriptQuery to match all scripts running in debuggee
-    // globals.
-    bool matchAllDebuggeeGlobals() {
-        MOZ_ASSERT(realms.count() == 0);
-        // Build our realm set from the debugger's set of debuggee globals.
-        for (WeakGlobalObjectSet::Range r = debugger->debuggees.all(); !r.empty(); r.popFront()) {
-            if (!addRealm(r.front()->realm())) {
-                ReportOutOfMemory(cx);
-                return false;
-            }
-        }
-        return true;
-    }
-};
-
 /*
  * A class for parsing 'findScripts' query arguments and searching for
  * scripts that match the criteria they represent.
  */
-class MOZ_STACK_CLASS Debugger::ScriptQuery : public Debugger::QueryBase
+class MOZ_STACK_CLASS Debugger::ScriptQuery
 {
   public:
     /* Construct a ScriptQuery to use matching scripts for |dbg|. */
-    ScriptQuery(JSContext* cx, Debugger* dbg)
-      : QueryBase(cx, dbg),
+    ScriptQuery(JSContext* cx, Debugger* dbg):
+        cx(cx),
+        debugger(dbg),
+        iterMarker(&cx->runtime()->gc),
+        realms(cx->zone()),
         url(cx),
         displayURLString(cx),
         hasSource(false),
@@ -4265,7 +4211,8 @@ class MOZ_STACK_CLASS Debugger::ScriptQuery : public Debugger::QueryBase
         innermostForRealm(cx->zone()),
         scriptVector(cx, ScriptVector(cx)),
         lazyScriptVector(cx, LazyScriptVector(cx)),
-        wasmInstanceVector(cx, WasmInstanceObjectVector(cx))
+        wasmInstanceVector(cx, WasmInstanceObjectVector(cx)),
+        oom(false)
     {}
 
     /*
@@ -4489,6 +4436,20 @@ class MOZ_STACK_CLASS Debugger::ScriptQuery : public Debugger::QueryBase
     }
 
   private:
+    /* The context in which we should do our work. */
+    JSContext* cx;
+
+    /* The debugger for which we conduct queries. */
+    Debugger* debugger;
+
+    /* Require the set of realms to stay fixed while the ScriptQuery is alive. */
+    gc::AutoEnterIteration iterMarker;
+
+    using RealmSet = HashSet<Realm*, DefaultHasher<Realm*>, ZoneAllocPolicy>;
+
+    /* A script must be in one of these realms to match the query. */
+    RealmSet realms;
+
     /* If this is a string, matching scripts have urls equal to it. */
     RootedValue url;
 
@@ -4538,6 +4499,39 @@ class MOZ_STACK_CLASS Debugger::ScriptQuery : public Debugger::QueryBase
      */
     Rooted<WasmInstanceObjectVector> wasmInstanceVector;
 
+    /* Indicates whether OOM has occurred while matching. */
+    bool oom;
+
+    bool addRealm(Realm* realm) {
+        return realms.put(realm);
+    }
+
+    /* Arrange for this ScriptQuery to match only scripts that run in |global|. */
+    bool matchSingleGlobal(GlobalObject* global) {
+        MOZ_ASSERT(realms.count() == 0);
+        if (!addRealm(global->realm())) {
+            ReportOutOfMemory(cx);
+            return false;
+        }
+        return true;
+    }
+
+    /*
+     * Arrange for this ScriptQuery to match all scripts running in debuggee
+     * globals.
+     */
+    bool matchAllDebuggeeGlobals() {
+        MOZ_ASSERT(realms.count() == 0);
+        // Build our realm set from the debugger's set of debuggee globals.
+        for (WeakGlobalObjectSet::Range r = debugger->debuggees.all(); !r.empty(); r.popFront()) {
+            if (!addRealm(r.front()->realm())) {
+                ReportOutOfMemory(cx);
+                return false;
+            }
+        }
+        return true;
+    }
+
     /*
      * Given that parseQuery or omittedQuery has been called, prepare to match
      * scripts. Set urlCString and displayURLChars as appropriate.
@@ -4771,160 +4765,6 @@ Debugger::findScripts(JSContext* cx, unsigned argc, Value* vp)
     return true;
 }
 
-/*
- * A class for searching sources for 'findSources'.
- */
-class MOZ_STACK_CLASS Debugger::SourceQuery : public Debugger::QueryBase
-{
-  public:
-    using SourceSet = JS::GCHashSet<JSObject*,
-                                    js::MovableCellHasher<JSObject*>,
-                                    ZoneAllocPolicy>;
-
-    SourceQuery(JSContext* cx, Debugger* dbg)
-      : QueryBase(cx, dbg),
-        sources(cx, SourceSet(cx->zone()))
-    {}
-
-    bool findSources() {
-        if (!matchAllDebuggeeGlobals())
-            return false;
-
-        Realm* singletonRealm = nullptr;
-        if (realms.count() == 1)
-            singletonRealm = realms.all().front();
-
-        // Search each realm for debuggee scripts.
-        MOZ_ASSERT(sources.empty());
-        oom = false;
-        IterateScripts(cx, singletonRealm, this, considerScript);
-        IterateLazyScripts(cx, singletonRealm, this, considerLazyScript);
-        if (oom) {
-            ReportOutOfMemory(cx);
-            return false;
-        }
-
-        // TODO: Until such time that wasm modules are real ES6 modules,
-        // unconditionally consider all wasm toplevel instance scripts.
-        for (WeakGlobalObjectSet::Range r = debugger->allDebuggees(); !r.empty(); r.popFront()) {
-            for (wasm::Instance* instance : r.front()->realm()->wasm.instances()) {
-                consider(instance->object());
-                if (oom) {
-                    ReportOutOfMemory(cx);
-                    return false;
-                }
-            }
-        }
-
-        return true;
-    }
-
-    Handle<SourceSet> foundSources() const {
-        return sources;
-    }
-
-  private:
-    Rooted<SourceSet> sources;
-
-    static void considerScript(JSRuntime* rt, void* data, JSScript* script,
-                               const JS::AutoRequireNoGC& nogc) {
-        SourceQuery* self = static_cast<SourceQuery*>(data);
-        self->consider(script, nogc);
-    }
-
-    static void considerLazyScript(JSRuntime* rt, void* data, LazyScript* lazyScript,
-                                   const JS::AutoRequireNoGC& nogc) {
-        SourceQuery* self = static_cast<SourceQuery*>(data);
-        self->consider(lazyScript, nogc);
-    }
-
-    void consider(JSScript* script, const JS::AutoRequireNoGC& nogc) {
-        if (oom || script->selfHosted())
-            return;
-        Realm* realm = script->realm();
-        if (!realms.has(realm))
-            return;
-
-        if (!script->sourceObject())
-            return;
-
-        ScriptSourceObject* source =
-            &UncheckedUnwrap(script->sourceObject())->as<ScriptSourceObject>();
-        if (!sources.put(source))
-            oom = true;
-    }
-
-    void consider(LazyScript* lazyScript, const JS::AutoRequireNoGC& nogc) {
-        if (oom)
-            return;
-        Realm* realm = lazyScript->realm();
-        if (!realms.has(realm))
-            return;
-
-        // If the script is already delazified, it should already be handled.
-        if (lazyScript->maybeScript())
-            return;
-
-        ScriptSourceObject* source = &lazyScript->sourceObject();
-        if (!sources.put(source))
-            oom = true;
-    }
-
-    void consider(WasmInstanceObject* instanceObject) {
-        if (oom)
-            return;
-
-        if (!sources.put(instanceObject))
-            oom = true;
-    }
-};
-
-static inline DebuggerSourceReferent
-AsSourceReferent(JSObject* obj)
-{
-    if (obj->is<ScriptSourceObject>()) {
-        return AsVariant(&obj->as<ScriptSourceObject>());
-    }
-    return AsVariant(&obj->as<WasmInstanceObject>());
-}
-
-/* static */ bool
-Debugger::findSources(JSContext* cx, unsigned argc, Value* vp)
-{
-    THIS_DEBUGGER(cx, argc, vp, "findSources", args, dbg);
-
-    if (gc::GCRuntime::temporaryAbortIfWasmGc(cx)) {
-        JS_ReportErrorASCII(cx, "API temporarily unavailable under wasm gc");
-        return false;
-    }
-
-    SourceQuery query(cx, dbg);
-    if (!query.findSources())
-        return false;
-
-    Handle<SourceQuery::SourceSet> sources(query.foundSources());
-
-    size_t resultLength = sources.count();
-    RootedArrayObject result(cx, NewDenseFullyAllocatedArray(cx, resultLength));
-    if (!result)
-        return false;
-
-    result->ensureDenseInitializedLength(cx, 0, resultLength);
-
-    size_t i = 0;
-    for (auto iter = sources.get().iter(); !iter.done(); iter.next()) {
-        Rooted<DebuggerSourceReferent> sourceReferent(cx, AsSourceReferent(iter.get()));
-        RootedObject sourceObject(cx, dbg->wrapVariantReferent(cx, sourceReferent));
-        if (!sourceObject)
-            return false;
-        result->setDenseElement(i, ObjectValue(*sourceObject));
-        i++;
-    }
-
-    args.rval().setObject(*result);
-    return true;
-}
-
 /*
  * A class for parsing 'findObjects' query arguments and searching for objects
  * that match the criteria they represent.
@@ -5341,7 +5181,6 @@ const JSFunctionSpec Debugger::methods[] = {
     JS_FN("getNewestFrame", Debugger::getNewestFrame, 0, 0),
     JS_FN("clearAllBreakpoints", Debugger::clearAllBreakpoints, 0, 0),
     JS_FN("findScripts", Debugger::findScripts, 1, 0),
-    JS_FN("findSources", Debugger::findSources, 1, 0),
     JS_FN("findObjects", Debugger::findObjects, 1, 0),
     JS_FN("findAllGlobals", Debugger::findAllGlobals, 0, 0),
     JS_FN("makeGlobalObjectReference", Debugger::makeGlobalObjectReference, 1, 0),
diff --git a/js/src/vm/Debugger.h b/js/src/vm/Debugger.h
index 94ff729b1e7e..ff8f18e4a6b6 100644
--- a/js/src/vm/Debugger.h
+++ b/js/src/vm/Debugger.h
@@ -566,9 +566,7 @@ class Debugger : private mozilla::LinkedListElement<Debugger>
     uint32_t traceLoggerScriptedCallsLastDrainedSize;
     uint32_t traceLoggerScriptedCallsLastDrainedIteration;
 
-    class QueryBase;
     class ScriptQuery;
-    class SourceQuery;
     class ObjectQuery;
 
     MOZ_MUST_USE bool addDebuggeeGlobal(JSContext* cx, Handle<GlobalObject*> obj);
@@ -720,7 +718,6 @@ class Debugger : private mozilla::LinkedListElement<Debugger>
     static bool getNewestFrame(JSContext* cx, unsigned argc, Value* vp);
     static bool clearAllBreakpoints(JSContext* cx, unsigned argc, Value* vp);
     static bool findScripts(JSContext* cx, unsigned argc, Value* vp);
-    static bool findSources(JSContext* cx, unsigned argc, Value* vp);
     static bool findObjects(JSContext* cx, unsigned argc, Value* vp);
     static bool findAllGlobals(JSContext* cx, unsigned argc, Value* vp);
     static bool makeGlobalObjectReference(JSContext* cx, unsigned argc, Value* vp);