diff --git a/layouts/partials/author-card.html b/layouts/partials/author-card.html
index 330ad37..839874b 100644
--- a/layouts/partials/author-card.html
+++ b/layouts/partials/author-card.html
@@ -3,18 +3,16 @@
 */ -}}
 <div class="flex items-center gap-4 py-6 border-t border-b border-zinc my-8">
   {{- $avatarRes := .Resources.GetMatch "avatar.*" -}}
-  {{- $avatarSrc := "" -}}
-  {{- with $avatarRes }}{{ $avatarSrc = .RelPermalink }}{{ else }}{{ with $.Params.avatar }}{{ $avatarSrc = . }}{{ end }}{{ end -}}
-  {{- with $avatarSrc -}}
-  <a href="{{ $.RelPermalink }}" class="flex-shrink-0">
-    <img
-      src="{{ . }}"
-      alt="{{ $.Params.name | default $.Title }}"
-      class="w-12 h-12 object-cover border border-zinc hover:border-heat transition-colors"
-      loading="lazy"
-    >
-  </a>
-  {{- end -}}
+  {{- if $avatarRes -}}
+    {{- $av := $avatarRes.Resize "96x webp" -}}
+    <a href="{{ $.RelPermalink }}" class="flex-shrink-0">
+      <img src="{{ $av.RelPermalink }}" alt="{{ $.Params.name | default $.Title }}" class="w-12 h-12 object-cover border border-zinc hover:border-heat transition-colors" width="{{ $av.Width }}" height="{{ $av.Height }}" loading="lazy" decoding="async">
+    </a>
+  {{- else -}}{{- with .Params.avatar -}}
+    <a href="{{ $.RelPermalink }}" class="flex-shrink-0">
+      <img src="{{ . }}" alt="{{ $.Params.name | default $.Title }}" class="w-12 h-12 object-cover border border-zinc hover:border-heat transition-colors" loading="lazy" decoding="async">
+    </a>
+  {{- end -}}{{- end -}}
   <div class="min-w-0">
     <a href="{{ .RelPermalink }}" class="label text-heat hover:text-frost transition-colors block mb-1">
       {{ .Params.name | default .Title }}
diff --git a/layouts/partials/img.html b/layouts/partials/img.html
new file mode 100644
index 0000000..be6fe09
--- /dev/null
+++ b/layouts/partials/img.html
@@ -0,0 +1,38 @@
+{{- /*
+  Renders a Hugo image resource as an optimised WebP <img> with responsive srcset.
+
+  Parameters:
+    res     — Hugo image resource (required)
+    widths  — slice of pixel widths to generate, e.g. (slice 600 1200)
+               default: (slice 800 1600)
+    sizes   — value for the <img sizes> attribute
+               default: "100vw"
+    class   — CSS classes applied to <img>
+    alt     — alt text (default "")
+    loading — "lazy" or "eager" (default "lazy")
+*/ -}}
+{{- $res     := .res -}}
+{{- $widths  := .widths  | default (slice 800 1600) -}}
+{{- $sizes   := .sizes   | default "100vw" -}}
+{{- $class   := .class   | default "" -}}
+{{- $alt     := .alt     | default "" -}}
+{{- $loading := .loading | default "lazy" -}}
+
+{{- $entries := slice -}}
+{{- $primary := $res -}}
+{{- range $i, $w := $widths -}}
+  {{- $img := $res.Resize (printf "%dx webp" $w) -}}
+  {{- $entries = $entries | append (printf "%s %dw" $img.RelPermalink $w) -}}
+  {{- if eq $i 0 -}}{{- $primary = $img -}}{{- end -}}
+{{- end -}}
+<img
+  class="{{ $class }}"
+  src="{{ $primary.RelPermalink }}"
+  srcset="{{ delimit $entries ", " }}"
+  sizes="{{ $sizes }}"
+  alt="{{ $alt }}"
+  width="{{ $primary.Width }}"
+  height="{{ $primary.Height }}"
+  loading="{{ $loading }}"
+  decoding="async"
+>
diff --git a/layouts/partials/post-card-large.html b/layouts/partials/post-card-large.html
index 290dcc0..1f6e8f8 100644
--- a/layouts/partials/post-card-large.html
+++ b/layouts/partials/post-card-large.html
@@ -10,7 +10,7 @@
     {{- if not $thumb -}}{{- $thumb = $post.Resources.GetMatch "01.png" -}}{{- end -}}
     <div class="card-media w-full h-full absolute inset-0">
       {{- if $thumb -}}
-        <img class="w-full h-full object-cover" src="{{ $thumb.RelPermalink }}" alt="{{ $post.Title }}" loading="lazy" decoding="async">
+        {{- partial "img.html" (dict "res" $thumb "widths" (slice 800 1200) "sizes" "(max-width: 768px) 100vw, 50vw" "class" "w-full h-full object-cover" "alt" $post.Title) -}}
       {{- else -}}{{- with $post.Params.banner -}}
         {{- partial "media.html" (dict "media" . "class" "w-full h-full object-cover") -}}
       {{- else -}}
diff --git a/layouts/partials/post-card.html b/layouts/partials/post-card.html
index 35ef1ba..c1fc03f 100644
--- a/layouts/partials/post-card.html
+++ b/layouts/partials/post-card.html
@@ -10,7 +10,7 @@
     {{- if not $thumb -}}{{- $thumb = $post.Resources.GetMatch "01.png" -}}{{- end -}}
     <div class="card-media aspect-editorial">
       {{- if $thumb -}}
-        <img class="w-full h-full object-cover" src="{{ $thumb.RelPermalink }}" alt="{{ $post.Title }}" loading="lazy" decoding="async">
+        {{- partial "img.html" (dict "res" $thumb "widths" (slice 600 1000) "sizes" "(max-width: 640px) 100vw, (max-width: 1024px) 50vw, 25vw" "class" "w-full h-full object-cover" "alt" $post.Title) -}}
       {{- else -}}{{- with $post.Params.banner -}}
         {{- partial "media.html" (dict "media" . "class" "w-full h-full object-cover") -}}
       {{- else -}}
@@ -40,16 +40,12 @@
         {{- $authorPage := site.GetPage (printf "authors/%s" .) -}}
         {{- with $authorPage -}}
           {{- $avRes := .Resources.GetMatch "avatar.*" -}}
-          {{- $avSrc := "" -}}
-          {{- with $avRes }}{{ $avSrc = .RelPermalink }}{{ else }}{{ with $.Params.avatar }}{{ $avSrc = . }}{{ end }}{{ end -}}
-          {{- with $avSrc -}}
-          <img
-            src="{{ . }}"
-            alt="{{ $authorPage.Params.name | default $authorPage.Title }}"
-            class="w-5 h-5 object-cover border border-smoke flex-shrink-0"
-            loading="lazy"
-          >
-          {{- end -}}
+          {{- if $avRes -}}
+            {{- $av := $avRes.Resize "64x webp" -}}
+            <img src="{{ $av.RelPermalink }}" alt="{{ $authorPage.Params.name | default $authorPage.Title }}" class="w-5 h-5 object-cover border border-smoke flex-shrink-0" width="{{ $av.Width }}" height="{{ $av.Height }}" loading="lazy" decoding="async">
+          {{- else -}}{{- with .Params.avatar -}}
+            <img src="{{ . }}" alt="{{ $authorPage.Params.name | default $authorPage.Title }}" class="w-5 h-5 object-cover border border-smoke flex-shrink-0" loading="lazy" decoding="async">
+          {{- end -}}{{- end -}}
           <span class="label text-fog">{{ .Params.name | default .Title }}</span>
           <span class="text-smoke" aria-hidden="true">/</span>
         {{- end -}}
diff --git a/layouts/posts/single.html b/layouts/posts/single.html
index 5ca942f..99a0942 100644
--- a/layouts/posts/single.html
+++ b/layouts/posts/single.html
@@ -73,7 +73,7 @@
 {{- if not $bannerImg -}}{{- $bannerImg = .Resources.GetMatch "01.png" -}}{{- end -}}
 {{- if $bannerImg -}}
 <div class="w-full overflow-hidden mb-16 md:mb-24" style="max-height: 75vh">
-  <img class="w-full object-cover" src="{{ $bannerImg.RelPermalink }}" alt="{{ .Title }}" loading="eager" decoding="async">
+  {{- partial "img.html" (dict "res" $bannerImg "widths" (slice 1200 1800) "sizes" "100vw" "class" "w-full object-cover" "alt" .Title "loading" "eager") -}}
 </div>
 {{- else -}}{{- with .Params.banner -}}
 <div class="w-full overflow-hidden mb-16 md:mb-24" style="max-height: 75vh">
@@ -116,7 +116,7 @@
         {{- if $video -}}
         <video class="w-full" src="{{ $video.RelPermalink }}" poster="{{ .RelPermalink }}" autoplay loop muted playsinline></video>
         {{- else -}}
-        <img class="w-full" src="{{ .RelPermalink }}" alt="" loading="lazy" decoding="async">
+        {{- partial "img.html" (dict "res" . "widths" (slice 800 1200) "sizes" "(max-width: 640px) 100vw, (max-width: 1024px) 50vw, 33vw" "class" "w-full") -}}
         {{- end -}}
       </div>
     </figure>