diff --git a/src/lib/kitty.c b/src/lib/kitty.c
index 2358f5d2f..777047f45 100644
--- a/src/lib/kitty.c
+++ b/src/lib/kitty.c
@@ -1,33 +1,54 @@
 #include "internal.h"
 
+static unsigned const char b64subs[] =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
 // we can only write 4KiB at a time
 static int
 write_kitty_data(FILE* fp, int linesize, int leny, int lenx, const uint32_t* data){
+#define KITTY_MAXLEN 4096 // 4096B maximum payload
   if(linesize % sizeof(*data)){
     return -1;
   }
-  // FIXME must write m=1 for initial chunks, m=0 for final (assuming > 1)
-  fprintf(fp, "\e_Gf=24,s=%d,v=%d;", lenx, leny);
-  // FIXME need to base64 encode payload. each 3B RGB goes to a 4B base64
-  for(int y = 0 ; y < leny ; ++y){
-    const uint32_t* line = data + (linesize / sizeof(*data)) * y;
-    for(int x = 0 ; x < lenx ; ++x){
+  int total = leny * lenx * 4; // 3B RGB -> 4B Base64, total bytes
+  int chunks = (total + (KITTY_MAXLEN - 1)) / KITTY_MAXLEN;
+  int totalout = 0; // total bytes of payload out
+  int y = 0;
+  int x = 0;
+  int targetout = 0;
+//fprintf(stderr, "total: %d chunks = %d, s=%d,v=%d\n", total, chunks, lenx, leny);
+  while(chunks--){
+    if(totalout == 0){
+      fprintf(fp, "\e_Gf=24,s=%d,v=%d,a=T%s;", lenx, leny, chunks > 1 ? ",m=1" : "");
+    }else{
+      fprintf(fp, "\e_Gm=%d;", chunks ? 1 : 0);
+    }
+    if((targetout += KITTY_MAXLEN) > total){
+      targetout = total;
+    }
+    while(totalout < targetout){
+      if(x == lenx){
+        x = 0;
+        ++y;
+      }
+      const uint32_t* line = data + (linesize / sizeof(*data)) * y;
       uint32_t pixel = line[x];
       unsigned r = ncpixel_r(pixel);
       unsigned g = ncpixel_g(pixel);
       unsigned b = ncpixel_b(pixel);
       unsigned char b64[4] = {
-        ((r & 0xfc) >> 2) + 'A',
-        ((r & 0x3 << 2) | ((g & 0xf0) >> 4)) + 'A',
-        (((g & 0xf) << 2) | ((b & 0xc0) >> 6)) + 'A',
-        (b & 0x3f) + 'A'
+        b64subs[((r & 0xfc) >> 2)],
+        b64subs[((r & 0x3 << 2) | ((g & 0xf0) >> 4))],
+        b64subs[(((g & 0xf) << 2) | ((b & 0xc0) >> 6))],
+        b64subs[(b & 0x3f)]
       };
-// this isn't the correct base64 distribution FIXME
-fprintf(stderr, "%u/%u/%u -> %c%c%c%c %u %u %u %u\n", r, g, b, b64[0], b64[1], b64[2], b64[3], b64[0], b64[1], b64[2], b64[3]);
+//fprintf(stderr, "%u/%u/%u -> %c%c%c%c %u %u %u %u\n", r, g, b, b64[0], b64[1], b64[2], b64[3], b64[0], b64[1], b64[2], b64[3]);
       fprintf(fp, "%c%c%c%c", b64[0], b64[1], b64[2], b64[3]);
+      totalout += 4;
+      ++x;
     }
+    fprintf(fp, "\e\\");
   }
-  fprintf(fp, "\e\\");
   if(fclose(fp) == EOF){
     return -1;
   }
@@ -65,6 +86,7 @@ int kitty_blit(ncplane* nc, int placey, int placex, int linesize,
                int leny, int lenx, unsigned cellpixx){
   (void)begy;
   (void)begx;
+//fprintf(stderr, "s=%d,v=%d\n", lenx, leny);
   int r = kitty_blit_inner(nc, placey, placex, linesize, leny, lenx, cellpixx, data);
   if(r < 0){
     return -1;