diff --git a/app/routes.py b/app/routes.py
index 743d1d0..7f41b81 100644
--- a/app/routes.py
+++ b/app/routes.py
@@ -8,7 +8,7 @@ from flask import abort, redirect, render_template, request, send_file, url_for
 from . import assembler, jobs, validation
 
 
-def _process_pair(job_dir, index, sdr_file, hdr_file):
+def _process_pair(job_dir, index, sdr_file, hdr_file, ignore_ig_resolution=False):
     """Runs one SDR/HDR pair through validation + assembly. Returns an item
     dict for the job report; never raises — failures are recorded in it."""
     name = hdr_file.filename or sdr_file.filename or f"pair {index}"
@@ -28,7 +28,7 @@ def _process_pair(job_dir, index, sdr_file, hdr_file):
     sdr_file.save(sdr_path)
     hdr_file.save(hdr_path)
 
-    ig_error = validation.instagram_resolution_error(sdr_path, hdr_path)
+    ig_error = validation.instagram_resolution_error(sdr_path, hdr_path, ignore_ig_resolution)
     if ig_error:
         for p in (sdr_path, hdr_path):
             p.unlink(missing_ok=True)
@@ -62,11 +62,13 @@ def register_routes(app):
         if len(sdr_files) != len(hdr_files):
             return render_template("index.html", error="Each pair needs both an SDR and an HDR file."), 400
 
+        ignore_ig_resolution = request.form.get("ignore_ig_resolution") == "on"
+
         job_id = uuid.uuid4().hex[:12]
         job_dir = jobs.new_job_dir(job_id)
 
         items = [
-            _process_pair(job_dir, i, sdr_file, hdr_file)
+            _process_pair(job_dir, i, sdr_file, hdr_file, ignore_ig_resolution)
             for i, (sdr_file, hdr_file) in enumerate(zip(sdr_files, hdr_files), start=1)
         ]
 
diff --git a/app/validation.py b/app/validation.py
index b0b6613..946aaea 100644
--- a/app/validation.py
+++ b/app/validation.py
@@ -42,9 +42,17 @@ def probe_dimensions(path: Path) -> tuple[int, int]:
         raise ValueError(f"could not read image dimensions ({e})") from e
 
 
-def instagram_resolution_error(sdr_path: Path, hdr_path: Path) -> str | None:
+def instagram_resolution_error(
+    sdr_path: Path, hdr_path: Path, ignore_ig_resolution: bool = False,
+) -> str | None:
     """Returns an error message if the pair doesn't meet Instagram's feed
-    requirements, otherwise None."""
+    requirements, otherwise None.
+
+    The dimension-match check always applies: mismatched SDR/HDR
+    dimensions misalign the gain map regardless of what platform the
+    result is for. ignore_ig_resolution skips only the exact-match check
+    against Instagram's own feed resolutions, for results meant for
+    somewhere other than Instagram."""
     try:
         sdr_w, sdr_h = probe_dimensions(sdr_path)
         hdr_w, hdr_h = probe_dimensions(hdr_path)
@@ -57,7 +65,7 @@ def instagram_resolution_error(sdr_path: Path, hdr_path: Path) -> str | None:
             "dimensions, otherwise the gain map will misalign."
         )
 
-    if (sdr_w, sdr_h) not in IG_RESOLUTIONS:
+    if not ignore_ig_resolution and (sdr_w, sdr_h) not in IG_RESOLUTIONS:
         allowed = ", ".join(f"{w}x{h} ({label})" for (w, h), label in IG_RESOLUTIONS.items())
         return f"Image is {sdr_w}x{sdr_h} — Instagram requires an exact match to one of: {allowed}."
 
diff --git a/static/style.css b/static/style.css
index b812a1b..7e14052 100644
--- a/static/style.css
+++ b/static/style.css
@@ -118,6 +118,18 @@ form { display: block; }
 
 .add-duo:hover { color: var(--text); border-color: var(--accent-dim); }
 
+.checkbox-row {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  margin: 1rem 0;
+  font-size: 0.85rem;
+  color: var(--text-muted);
+  cursor: pointer;
+}
+
+.checkbox-row input { cursor: pointer; }
+
 .dropzones {
   display: grid;
   grid-template-columns: 1fr 1fr;
diff --git a/templates/index.html b/templates/index.html
index 321a298..4c105da 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -40,16 +40,23 @@
 
         <button type="button" class="add-duo" id="add-duo">+ Add another pair</button>
 
+        <label class="checkbox-row">
+          <input type="checkbox" name="ignore_ig_resolution">
+          Process anyway if the resolution doesn't match Instagram's feed sizes
+        </label>
+
         <button class="run" type="submit">Assemble the HDR</button>
       </form>
     </div>
 
     <p class="footnote">
-      Each pair's files must have identical dimensions, matching exactly one of Instagram's feed
-      resolutions: <strong>1080x1080</strong> (1:1), <strong>1080x1350</strong> (4:5), or
-      <strong>1080x566</strong> (1.91:1). Assembling more than one pair downloads as a <code>.zip</code>.
-      HDR can be a regular gain-map JPEG or Lightroom's 32-bit float linear HDR TIFF export; a
-      TIFF HDR file gives a more precise result than the JPEG gain-map route.
+      Each pair's files must have identical dimensions. By default that must also match one of
+      Instagram's feed resolutions exactly: <strong>1080x1080</strong> (1:1),
+      <strong>1080x1350</strong> (4:5), or <strong>1080x566</strong> (1.91:1); check the box above
+      to skip that check for results meant for somewhere other than Instagram. Assembling more
+      than one pair downloads as a <code>.zip</code>. HDR can be a regular gain-map JPEG or
+      Lightroom's 32-bit float linear HDR TIFF export; a TIFF HDR file gives a more precise result
+      than the JPEG gain-map route.
     </p>
     <p class="version">Instagram HDR Assembler v{{ app_version }}</p>
   </div>