diff --git a/src/render.cpp b/src/render.cpp
index 93ea1a3..92283fd 100644
--- a/src/render.cpp
+++ b/src/render.cpp
@@ -395,11 +395,9 @@ void update_and_render(Arena *arena, App_State &app, f32 delta_time_ms)
 }
 
 internal
-Term_Viewer make_term_viewer(u16 n_cols)
+Term_Viewer make_term_viewer()
 {
   Term_Viewer viewer {};
-  viewer.max_cols = n_cols ? n_cols : 32;
-  
   viewer.col_key        = ACol_Green;
   viewer.col_page_start = ACol_Bright_Magenta;
   viewer.col_checksum   = ACol_Yellow;
@@ -485,7 +483,7 @@ String8 render_legend_to_string(Arena *arena, const Term_Viewer &viewer, const A
 internal
 String8 render_range_to_string(Arena *arena, App_State &app, u64 len, u64 n_cols)
 {
-  Term_Viewer viewer = make_term_viewer(n_cols);
+  Term_Viewer viewer = make_term_viewer();
 
   String8 legend = render_legend_to_string(arena, viewer, app);
 
@@ -496,18 +494,34 @@ String8 render_range_to_string(Arena *arena, App_State &app, u64 len, u64 n_cols
   String8 ntpl_desc = rntuple_description(scratch.arena, app.rndata);
   String8 header_str = push_str8f(scratch.arena, "RNTuple '%s' (%s) from file \"%s\"",
                                   app.ntpl_name.c(), ntpl_desc.c(), app.inspected_file.name.c());
+
+  if (n_cols == 0)
+    n_cols = 32;
+  u64 n_lines = len / n_cols;
+  u64 max_addr = app.inspected_file.size;
+
+  // Calculate how much space do we need to fix line addr numbers.
+  // The biggest address is gonna take up the most space
+  const f32 RECP_LOG_16 = 0.360673760222f;
+  // NOTE: +1 for the ":"
+  u64 max_addr_len = 1 + ceilf(logf(max_addr + 1) * RECP_LOG_16);
+  const u64 n_spaces_after_line_addr = 3;
+  u64 line_addr_size = (max_addr_len + n_spaces_after_line_addr) * n_lines;
+  String8 line_addr_fmt = push_str8f(scratch.arena, "%%0%dlX:", max_addr_len - 1);
   
   // NOTE: +3 because we need 2 chars for each byte + 1 whitespace.
   u64 buf_size = (ACOL_MAX_LEN + 3) * len;
-  u64 n_newlines = len / viewer.max_cols;
-  buf_size += n_newlines;
+  buf_size += n_lines; // one newline per line
+  buf_size += n_lines * ACOL_MAX_LEN; // reset color every line
+  buf_size += line_addr_size;
   buf_size += 1; // initial newline
   buf_size += header_str.size;
-  buf_size += 2; // two newlines
-  buf_size += 2; // two newlines
+  buf_size += 2; // two newlines after header
+  buf_size += 2; // two newlines before legend
   buf_size += legend.size;
   buf_size += 1; // trailing zero
-  u8 *buf = arena_push_array_nozero<u8>(arena, buf_size);
+  u64 arena_start_pos = arena_pos(arena);
+  char *buf = arena_push_array_nozero<char>(arena, buf_size);
   buf[len] = 0;
 
   u64 start = app.viewer.base_display_addr;
@@ -516,11 +530,10 @@ String8 render_range_to_string(Arena *arena, App_State &app, u64 len, u64 n_cols
   app.last_pinfo = &invalid_pinfo;
 
   const u8 *data = app.inspected_file.mem;
-  u64 max_addr = app.inspected_file.size;
   assert(start <= max_addr);
   len = min(len, max_addr - start);
   
-  u8 *cur = buf;
+  char *cur = buf;
   *cur++ = '\n';
 
   // header
@@ -529,6 +542,13 @@ String8 render_range_to_string(Arena *arena, App_State &app, u64 len, u64 n_cols
   *cur++ = '\n';
   *cur++ = '\n';
   
+  // first line addr
+  cur += sprintf(cur, line_addr_fmt.c(), start);
+  for (u32 i = 0; i < n_spaces_after_line_addr; ++i)
+    *cur++ = ' ';
+  
+  String8 col_none = ansi_color_table[ACol_None];
+
   for (u64 i = 0; i < len; ++i) {
     u64 off = start + i;
 
@@ -542,12 +562,17 @@ String8 render_range_to_string(Arena *arena, App_State &app, u64 len, u64 n_cols
     cur += acol_str.size;
 
     /// Write the human-readable byte
-    String8 byte_str = push_str8f(scratch.arena, "%02X ", data[off]);
-    memcpy(cur, byte_str.str, byte_str.size);
-    cur += byte_str.size;
+    cur += sprintf(cur, "%02X ", data[off]);
 
-    if ((i + 1) % viewer.max_cols == 0)
+    // new line
+    if ((i + 1) % n_cols == 0) {
       *cur++ = '\n';
+      memcpy(cur, col_none.c(), col_none.size);
+      cur += col_none.size;
+      cur += sprintf(cur, line_addr_fmt.c(), off + 1);
+      for (u32 i = 0; i < n_spaces_after_line_addr; ++i)
+        *cur++ = ' ';
+    }
 
     assert((u64)(cur - buf) < (u64)buf_size);
   }
@@ -559,5 +584,8 @@ String8 render_range_to_string(Arena *arena, App_State &app, u64 len, u64 n_cols
 
   *cur = 0;
 
-  return { buf, (u64)(cur - buf) };
+  u64 len_used = (u64)(cur - buf);
+  arena_pop_to(arena, arena_start_pos + len_used);
+
+  return { (u8 *)buf, len_used };
 }
diff --git a/src/rntviewer.cpp b/src/rntviewer.cpp
index ac4852e..b4bfc67 100644
--- a/src/rntviewer.cpp
+++ b/src/rntviewer.cpp
@@ -13,6 +13,8 @@
 
 #include <cstdio>
 #include <cstdint>
+#include <cmath>
+#include <cstring>
 #include <byteswap.h>
 #include <chrono>