diff --git a/release/scripts/startup/bl_ui/space_sequencer.py b/release/scripts/startup/bl_ui/space_sequencer.py
index 76c579f221f..8852ff84fe0 100644
--- a/release/scripts/startup/bl_ui/space_sequencer.py
+++ b/release/scripts/startup/bl_ui/space_sequencer.py
@@ -929,6 +929,7 @@ class SEQUENCER_PT_proxy(SequencerButtonsPanel, Panel):
             row.prop(strip.proxy, "build_50")
             row.prop(strip.proxy, "build_75")
             row.prop(strip.proxy, "build_100")
+            layout.prop(strip.proxy, "use_overwrite");
 
             col = layout.column()
             col.label(text="Build JPEG quality")
diff --git a/source/blender/blenkernel/intern/sequencer.c b/source/blender/blenkernel/intern/sequencer.c
index 903c660dc97..f63f4cf86ae 100644
--- a/source/blender/blenkernel/intern/sequencer.c
+++ b/source/blender/blenkernel/intern/sequencer.c
@@ -1290,6 +1290,7 @@ typedef struct SeqIndexBuildContext {
 	int tc_flags;
 	int size_flags;
 	int quality;
+	bool overwrite;
 
 	Main *bmain;
 	Scene *scene;
@@ -1481,7 +1482,8 @@ static ImBuf *seq_proxy_fetch(const SeqRenderData *context, Sequence *seq, int c
 	}
 }
 
-static void seq_proxy_build_frame(const SeqRenderData *context, Sequence *seq, int cfra, int proxy_render_size)
+static void seq_proxy_build_frame(const SeqRenderData *context, Sequence *seq, int cfra,
+                                  int proxy_render_size, const bool overwrite)
 {
 	char name[PROXY_MAXFILE];
 	int quality;
@@ -1493,6 +1495,10 @@ static void seq_proxy_build_frame(const SeqRenderData *context, Sequence *seq, i
 		return;
 	}
 
+	if (!overwrite && BLI_exists(name)) {
+		return;
+	}
+
 	ibuf_tmp = seq_render_strip(context, seq, cfra);
 
 	rectx = (proxy_render_size * ibuf_tmp->x) / 100;
@@ -1546,6 +1552,7 @@ SeqIndexBuildContext *BKE_sequencer_proxy_rebuild_context(Main *bmain, Scene *sc
 	context->tc_flags   = nseq->strip->proxy->build_tc_flags;
 	context->size_flags = nseq->strip->proxy->build_size_flags;
 	context->quality    = nseq->strip->proxy->quality;
+	context->overwrite = (nseq->strip->proxy->build_flags & SEQ_PROXY_SKIP_EXISTING) == 0;
 
 	context->bmain = bmain;
 	context->scene = scene;
@@ -1557,7 +1564,8 @@ SeqIndexBuildContext *BKE_sequencer_proxy_rebuild_context(Main *bmain, Scene *sc
 
 		if (nseq->anim) {
 			context->index_context = IMB_anim_index_rebuild_context(nseq->anim,
-			        context->tc_flags, context->size_flags, context->quality);
+			        context->tc_flags, context->size_flags, context->quality,
+			        context->overwrite);
 		}
 	}
 
@@ -1566,6 +1574,7 @@ SeqIndexBuildContext *BKE_sequencer_proxy_rebuild_context(Main *bmain, Scene *sc
 
 void BKE_sequencer_proxy_rebuild(SeqIndexBuildContext *context, short *stop, short *do_update, float *progress)
 {
+	const bool overwrite = context->overwrite;
 	SeqRenderData render_context;
 	Sequence *seq = context->seq;
 	Scene *scene = context->scene;
@@ -1602,16 +1611,16 @@ void BKE_sequencer_proxy_rebuild(SeqIndexBuildContext *context, short *stop, sho
 
 	for (cfra = seq->startdisp + seq->startstill;  cfra < seq->enddisp - seq->endstill; cfra++) {
 		if (context->size_flags & IMB_PROXY_25) {
-			seq_proxy_build_frame(&render_context, seq, cfra, 25);
+			seq_proxy_build_frame(&render_context, seq, cfra, 25, overwrite);
 		}
 		if (context->size_flags & IMB_PROXY_50) {
-			seq_proxy_build_frame(&render_context, seq, cfra, 50);
+			seq_proxy_build_frame(&render_context, seq, cfra, 50, overwrite);
 		}
 		if (context->size_flags & IMB_PROXY_75) {
-			seq_proxy_build_frame(&render_context, seq, cfra, 75);
+			seq_proxy_build_frame(&render_context, seq, cfra, 75, overwrite);
 		}
 		if (context->size_flags & IMB_PROXY_100) {
-			seq_proxy_build_frame(&render_context, seq, cfra, 100);
+			seq_proxy_build_frame(&render_context, seq, cfra, 100, overwrite);
 		}
 
 		*progress = (float) (cfra - seq->startdisp - seq->startstill) / (seq->enddisp - seq->endstill - seq->startdisp - seq->startstill);
diff --git a/source/blender/editors/space_clip/clip_ops.c b/source/blender/editors/space_clip/clip_ops.c
index e3d45a297a7..231677688ad 100644
--- a/source/blender/editors/space_clip/clip_ops.c
+++ b/source/blender/editors/space_clip/clip_ops.c
@@ -1342,7 +1342,8 @@ static int clip_rebuild_proxy_exec(bContext *C, wmOperator *UNUSED(op))
 
 	if (clip->anim) {
 		pj->index_context = IMB_anim_index_rebuild_context(clip->anim, clip->proxy.build_tc_flag,
-		                                                   clip->proxy.build_size_flag, clip->proxy.quality);
+		                                                   clip->proxy.build_size_flag, clip->proxy.quality,
+		                                                   true);
 	}
 
 	WM_jobs_customdata_set(wm_job, pj, proxy_freejob);
diff --git a/source/blender/imbuf/IMB_imbuf.h b/source/blender/imbuf/IMB_imbuf.h
index ce6a7eb1c47..b0250a142ff 100644
--- a/source/blender/imbuf/IMB_imbuf.h
+++ b/source/blender/imbuf/IMB_imbuf.h
@@ -236,11 +236,14 @@ void IMB_anim_set_index_dir(struct anim *anim, const char *dir);
 int IMB_anim_index_get_frame_index(struct anim *anim, IMB_Timecode_Type tc,
                                    int position);
 
+IMB_Proxy_Size IMB_anim_proxy_get_existing(struct anim *anim);
+
 struct IndexBuildContext;
 
 /* prepare context for proxies/imecodes builder */
 struct IndexBuildContext *IMB_anim_index_rebuild_context(struct anim *anim, IMB_Timecode_Type tcs_in_use,
-                                                         IMB_Proxy_Size proxy_sizes_in_use, int quality);
+                                                         IMB_Proxy_Size proxy_sizes_in_use, int quality,
+                                                         const bool overwite);
 
 /* will rebuild all used indices and proxies at once */
 void IMB_anim_index_rebuild(struct IndexBuildContext *context,
diff --git a/source/blender/imbuf/intern/indexer.c b/source/blender/imbuf/intern/indexer.c
index e067cd64022..856f870fb38 100644
--- a/source/blender/imbuf/intern/indexer.c
+++ b/source/blender/imbuf/intern/indexer.c
@@ -1148,19 +1148,30 @@ static void index_rebuild_fallback(FallbackIndexBuilderContext *context,
  * ---------------------------------------------------------------------- */
 
 IndexBuildContext *IMB_anim_index_rebuild_context(struct anim *anim, IMB_Timecode_Type tcs_in_use,
-                                                  IMB_Proxy_Size proxy_sizes_in_use, int quality)
+                                                  IMB_Proxy_Size proxy_sizes_in_use, int quality,
+                                                  const bool overwrite)
 {
 	IndexBuildContext *context = NULL;
+	IMB_Proxy_Size proxy_sizes_to_build = proxy_sizes_in_use;
+
+	if (!overwrite) {
+		IMB_Proxy_Size built_proxies = IMB_anim_proxy_get_existing(anim);
+		proxy_sizes_to_build &= ~built_proxies;
+	}
+
+	if (proxy_sizes_to_build == 0) {
+		return NULL;
+	}
 
 	switch (anim->curtype) {
 #ifdef WITH_FFMPEG
 		case ANIM_FFMPEG:
-			context = index_ffmpeg_create_context(anim, tcs_in_use, proxy_sizes_in_use, quality);
+			context = index_ffmpeg_create_context(anim, tcs_in_use, proxy_sizes_to_build, quality);
 			break;
 #endif
 #ifdef WITH_AVI
 		default:
-			context = index_fallback_create_context(anim, tcs_in_use, proxy_sizes_in_use, quality);
+			context = index_fallback_create_context(anim, tcs_in_use, proxy_sizes_to_build, quality);
 			break;
 #endif
 	}
@@ -1304,3 +1315,18 @@ int IMB_anim_index_get_frame_index(struct anim *anim, IMB_Timecode_Type tc,
 	return IMB_indexer_get_frame_index(idx, position);
 }
 
+IMB_Proxy_Size IMB_anim_proxy_get_existing(struct anim *anim)
+{
+	const int num_proxy_sizes = IMB_PROXY_MAX_SLOT;
+	IMB_Proxy_Size existing = 0;
+	int i;
+	for (i = 0; i < num_proxy_sizes; ++i) {
+		IMB_Proxy_Size proxy_size = proxy_sizes[i];
+		char filename[FILE_MAX];
+		get_proxy_filename(anim, proxy_size, filename, false);
+		if (BLI_exists(filename)) {
+			existing |= proxy_size;
+		}
+	}
+	return existing;
+}
diff --git a/source/blender/makesdna/DNA_sequence_types.h b/source/blender/makesdna/DNA_sequence_types.h
index 20678bdae49..c6748cca8e1 100644
--- a/source/blender/makesdna/DNA_sequence_types.h
+++ b/source/blender/makesdna/DNA_sequence_types.h
@@ -94,6 +94,8 @@ typedef struct StripProxy {
 	                       // to build
 	short build_tc_flags;  // time code flags (see below) of all tc indices
 	                       // to build
+	short build_flags;
+	char pad[6];
 } StripProxy;
 
 typedef struct Strip {
@@ -398,6 +400,11 @@ enum {
 #define SEQ_PROXY_TC_RECORD_RUN_NO_GAPS         8
 #define SEQ_PROXY_TC_ALL                        15
 
+/* SeqProxy->build_flags */
+enum {
+	SEQ_PROXY_SKIP_EXISTING = 1,
+};
+
 /* seq->alpha_mode */
 enum {
 	SEQ_ALPHA_STRAIGHT = 0,
diff --git a/source/blender/makesrna/intern/rna_sequencer.c b/source/blender/makesrna/intern/rna_sequencer.c
index dda0e8493d9..d4a98fe8b5d 100644
--- a/source/blender/makesrna/intern/rna_sequencer.c
+++ b/source/blender/makesrna/intern/rna_sequencer.c
@@ -1187,6 +1187,10 @@ static void rna_def_strip_proxy(BlenderRNA *brna)
 
 	RNA_def_property_update(prop, NC_SCENE | ND_SEQUENCER, "rna_SequenceProxy_update");
 
+	prop = RNA_def_property(srna, "use_overwrite", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_negative_sdna(prop, NULL, "build_flags", SEQ_PROXY_SKIP_EXISTING);
+	RNA_def_property_ui_text(prop, "Overwite", "Overwrite existing proxy files when building");
+
 	prop = RNA_def_property(srna, "build_25", PROP_BOOLEAN, PROP_NONE);
 	RNA_def_property_boolean_sdna(prop, NULL, "build_size_flags", SEQ_PROXY_IMAGE_SIZE_25);
 	RNA_def_property_ui_text(prop, "25%", "Build 25% proxy resolution");