diff --git a/src/app.d.ts b/src/app.d.ts
index 4462d62..6040841 100644
--- a/src/app.d.ts
+++ b/src/app.d.ts
@@ -27,6 +27,13 @@ declare global {
       profiles: MaintenanceProfile;
       groups: TagGroup;
     }
+
+    interface ImageURIs {
+      full: string;
+      large: string;
+      medium: string;
+      small: string;
+    }
   }
 }
 
diff --git a/src/lib/components/FullscreenViewer.js b/src/lib/components/FullscreenViewer.js
index 204f287..ee8b939 100644
--- a/src/lib/components/FullscreenViewer.js
+++ b/src/lib/components/FullscreenViewer.js
@@ -1,13 +1,14 @@
 import {BaseComponent} from "$lib/components/base/BaseComponent.js";
+import MiscSettings from "$lib/extension/settings/MiscSettings.ts";
 
 export class FullscreenViewer extends BaseComponent {
   /** @type {HTMLVideoElement} */
   #videoElement = document.createElement('video');
   /** @type {HTMLImageElement} */
   #imageElement = document.createElement('img');
-
   #spinnerElement = document.createElement('i');
-
+  #sizeSelectorElement = document.createElement('select');
+  #closeButtonElement = document.createElement('i');
   /** @type {number|null} */
   #touchId = null;
   /** @type {number|null} */
@@ -16,15 +17,33 @@ export class FullscreenViewer extends BaseComponent {
   #startY = null;
   /** @type {boolean|null} */
   #isClosingSwipeStarted = null;
+  #isSizeFetched = false;
+  /** @type {App.ImageURIs|null} */
+  #currentURIs = null;
 
   /**
    * @protected
    */
   build() {
     this.container.classList.add('fullscreen-viewer');
-    this.container.append(this.#spinnerElement);
+
+    this.container.append(
+      this.#spinnerElement,
+      this.#sizeSelectorElement,
+      this.#closeButtonElement,
+    );
 
     this.#spinnerElement.classList.add('spinner', 'fa', 'fa-circle-notch', 'fa-spin');
+    this.#closeButtonElement.classList.add('close', 'fa', 'fa-xmark');
+    this.#sizeSelectorElement.classList.add('size-selector', 'input');
+
+    for (const [sizeKey, sizeName] of Object.entries(FullscreenViewer.#previewSizes)) {
+      const sizeOptionElement = document.createElement('option');
+      sizeOptionElement.value = sizeKey;
+      sizeOptionElement.innerText = sizeName;
+
+      this.#sizeSelectorElement.append(sizeOptionElement);
+    }
   }
 
   /**
@@ -40,6 +59,12 @@ export class FullscreenViewer extends BaseComponent {
 
     this.#videoElement.addEventListener('loadeddata', this.#onLoaded.bind(this));
     this.#imageElement.addEventListener('load', this.#onLoaded.bind(this));
+    this.#sizeSelectorElement.addEventListener('click', event => event.stopPropagation());
+
+    FullscreenViewer.#miscSettings
+      .resolveFullscreenViewerPreviewSize()
+      .then(this.#onSizeResolved.bind(this))
+      .then(this.#watchForSizeSelectionChanges.bind(this));
   }
 
   #onLoaded() {
@@ -163,7 +188,49 @@ export class FullscreenViewer extends BaseComponent {
     }
   }
 
+  /**
+   * @param {import("$lib/extension/settings/MiscSettings.js").FullscreenViewerSize} size
+   */
+  #onSizeResolved(size) {
+    this.#sizeSelectorElement.value = size;
+    this.#isSizeFetched = true;
+
+    this.emit('size-loaded');
+  }
+
+  #watchForSizeSelectionChanges() {
+    let lastActiveSize = this.#sizeSelectorElement.value;
+
+    FullscreenViewer.#miscSettings.subscribe(settings => {
+      const targetSize = settings.fullscreenViewerSize;
+
+      if (!targetSize || lastActiveSize === targetSize) {
+        return;
+      }
+
+      lastActiveSize = targetSize;
+      this.#sizeSelectorElement.value = targetSize;
+    });
+
+    this.#sizeSelectorElement.addEventListener('input', () => {
+      const targetSize = this.#sizeSelectorElement.value;
+
+      if (this.#currentURIs) {
+        void this.show(this.#currentURIs);
+      }
+
+      if (!targetSize || targetSize === lastActiveSize || !(targetSize in FullscreenViewer.#previewSizes)) {
+        return;
+      }
+
+      lastActiveSize = targetSize;
+      void FullscreenViewer.#miscSettings.setFullscreenViewerPreviewSize(targetSize);
+    });
+  }
+
   #close() {
+    this.#currentURIs = null;
+
     this.container.classList.remove(FullscreenViewer.#shownState);
     document.body.style.overflow = null;
 
@@ -175,9 +242,44 @@ export class FullscreenViewer extends BaseComponent {
   }
 
   /**
-   * @param {string} url
+   * @param {App.ImageURIs} imageUris
+   * @return {Promise<string|null>}
    */
-  show(url) {
+  async #resolveCurrentSelectedSizeUrl(imageUris) {
+    if (!this.#isSizeFetched) {
+      await new Promise(resolve => this.on('size-loaded', resolve))
+    }
+
+    let targetSize = this.#sizeSelectorElement.value;
+
+    if (!imageUris.hasOwnProperty(targetSize)) {
+      targetSize = FullscreenViewer.#fallbackSize;
+    }
+
+    if (!imageUris.hasOwnProperty(targetSize)) {
+      targetSize = Object.keys(imageUris)[0];
+    }
+
+    if (!targetSize) {
+      return null;
+    }
+
+    return imageUris[targetSize];
+  }
+
+  /**
+   * @param {App.ImageURIs} imageUris
+   */
+  async show(imageUris) {
+    this.#currentURIs = imageUris;
+
+    const url = await this.#resolveCurrentSelectedSizeUrl(imageUris);
+
+    if (!url) {
+      console.warn('Failed to resolve media for the viewer!');
+      return;
+    }
+
     this.container.classList.add('loading');
 
     requestAnimationFrame(() => {
@@ -214,9 +316,23 @@ export class FullscreenViewer extends BaseComponent {
     return url.endsWith('.mp4') || url.endsWith('.webm');
   }
 
+  static #miscSettings = new MiscSettings();
+
   static #offsetProperty = '--offset';
   static #opacityProperty = '--opacity';
   static #shownState = 'shown';
   static #swipeState = 'swiped';
   static #minRequiredDistance = 50;
+
+  /**
+   * @type {Record<import("$lib/extension/settings/MiscSettings.js").FullscreenViewerSize, string>}
+   */
+  static #previewSizes = {
+    full: 'Full',
+    large: 'Large',
+    medium: 'Medium',
+    small: 'Small'
+  }
+
+  static #fallbackSize = 'large';
 }
diff --git a/src/lib/components/ImageShowFullscreenButton.js b/src/lib/components/ImageShowFullscreenButton.js
index f0cd8c7..2f8c6e3 100644
--- a/src/lib/components/ImageShowFullscreenButton.js
+++ b/src/lib/components/ImageShowFullscreenButton.js
@@ -33,7 +33,7 @@ export class ImageShowFullscreenButton extends BaseComponent {
         })
         .then(() => {
           ImageShowFullscreenButton.#miscSettings.subscribe(settings => {
-            this.#isFullscreenButtonEnabled = settings.fullscreenViewer;
+            this.#isFullscreenButtonEnabled = settings.fullscreenViewer ?? true;
             this.#updateFullscreenButtonVisibility();
           })
         })
@@ -47,7 +47,7 @@ export class ImageShowFullscreenButton extends BaseComponent {
   #onButtonClicked() {
     ImageShowFullscreenButton
       .#resolveViewer()
-      .show(this.#mediaBoxTools.mediaBox.imageLinks.large);
+      .show(this.#mediaBoxTools.mediaBox.imageLinks);
   }
 
   /**
diff --git a/src/lib/components/MediaBoxWrapper.js b/src/lib/components/MediaBoxWrapper.js
index cc4c6a2..5fb1a3f 100644
--- a/src/lib/components/MediaBoxWrapper.js
+++ b/src/lib/components/MediaBoxWrapper.js
@@ -56,7 +56,7 @@ export class MediaBoxWrapper extends BaseComponent {
   }
 
   /**
-   * @return {ImageURIs}
+   * @return {App.ImageURIs}
    */
   get imageLinks() {
     return JSON.parse(this.#thumbnailContainer.dataset.uris);
@@ -100,10 +100,3 @@ export function calculateMediaBoxesPositions(mediaBoxesList) {
     }
   })
 }
-
-/**
- * @typedef {Object} ImageURIs
- * @property {string} full
- * @property {string} large
- * @property {string} small
- */
diff --git a/src/lib/extension/settings/MiscSettings.ts b/src/lib/extension/settings/MiscSettings.ts
index 94ea7d2..1e0e76d 100644
--- a/src/lib/extension/settings/MiscSettings.ts
+++ b/src/lib/extension/settings/MiscSettings.ts
@@ -1,7 +1,10 @@
 import CacheableSettings from "$lib/extension/base/CacheableSettings.ts";
 
+export type FullscreenViewerSize = 'small' | 'medium' | 'large' | 'full';
+
 interface MiscSettingsFields {
   fullscreenViewer: boolean;
+  fullscreenViewerSize: FullscreenViewerSize;
 }
 
 export default class MiscSettings extends CacheableSettings<MiscSettingsFields> {
@@ -13,7 +16,15 @@ export default class MiscSettings extends CacheableSettings<MiscSettingsFields>
     return this._resolveSetting("fullscreenViewer", true);
   }
 
+  async resolveFullscreenViewerPreviewSize() {
+    return this._resolveSetting('fullscreenViewerSize', 'large');
+  }
+
   async setFullscreenViewerEnabled(isEnabled: boolean) {
     return this._writeSetting("fullscreenViewer", isEnabled);
   }
+
+  async setFullscreenViewerPreviewSize(size: FullscreenViewerSize | string) {
+    return this._writeSetting('fullscreenViewerSize', size as FullscreenViewerSize);
+  }
 }
diff --git a/src/styles/content/listing.scss b/src/styles/content/listing.scss
index 37804f5..a6ec9e9 100644
--- a/src/styles/content/listing.scss
+++ b/src/styles/content/listing.scss
@@ -199,6 +199,30 @@
     transition: opacity .25s ease;
   }
 
+  .size-selector {
+    position: absolute;
+    top: 5px;
+    left: 5px;
+    z-index: 1;
+  }
+
+  .close {
+    position: absolute;
+    top: 5px;
+    right: 5px;
+    z-index: 1;
+    padding: 5px;
+    background-color: colors.$text;
+    color: colors.$background;
+    font-size: 20px;
+    line-height: 20px;
+    width: 20px;
+    height: 20px;
+    text-align: center;
+    display: block;
+    cursor: pointer;
+  }
+
   &.shown {
     opacity: var(--opacity, 1);
     pointer-events: initial;