diff --git a/lib/phoenix_kit/migrations/postgres.ex b/lib/phoenix_kit/migrations/postgres.ex
index 6ee4ecd31..5208fa954 100644
--- a/lib/phoenix_kit/migrations/postgres.ex
+++ b/lib/phoenix_kit/migrations/postgres.ex
@@ -158,24 +158,43 @@ defmodule PhoenixKit.Migrations.Postgres do
   - Configurable strictness: Can log warnings or force re-authentication
   - Performance indexes for efficient fingerprint verification
 
-  ### V24 - File Checksum Unique Index ⚡ LATEST
+  ### V24 - File Checksum Unique Index
   - Unique index on phoenix_kit_files.checksum for O(1) duplicate detection
   - Enables automatic deduplication of uploaded files
   - Prevents redundant storage of identical files
   - Improves performance of duplicate file lookups
 
+  ### V25 - Aspect Ratio Control for Dimensions
+  - Adds maintain_aspect_ratio boolean column to phoenix_kit_storage_dimensions
+  - Allows choosing between aspect ratio preservation (width-only) or fixed dimensions
+  - Per-dimension control for responsive sizing vs exact crops
+  - Defaults to maintaining aspect ratio for all dimensions
+
+  ### V26 - Rename Checksum Fields & Per-User Deduplication ⚡ LATEST
+  - Renames `checksum` to `file_checksum` (clearer naming)
+  - Removes unique index on file_checksum (allows same file from different users)
+  - Adds `user_file_checksum` column (SHA256 of user_id + file_checksum)
+  - Creates unique index on user_file_checksum for per-user duplicate detection
+  - Same user cannot upload same file twice (enforced by user_file_checksum)
+  - Different users CAN upload same file (different user_file_checksum values)
+  - Preserves file_checksum field for popularity analytics across all users
+  - Clearer naming convention: file_checksum vs user_file_checksum
+
   ## Migration Paths
 
   ### Fresh Installation (0 → Current)
-  Runs all migrations V01 through V24 in sequence.
+  Runs all migrations V01 through V26 in sequence.
 
   ### Incremental Updates
-  - V01 → V24: Runs V02 through V24 in sequence
-  - V23 → V24: Runs V24 only (adds file checksum unique index)
-  - V22 → V24: Runs V23 and V24 in sequence
-  - V20 → V24: Runs V21, V22, V23, and V24 in sequence
+  - V01 → V26: Runs V02 through V26 in sequence
+  - V25 → V26: Runs V26 only (adds per-user file hash)
+  - V24 → V26: Runs V25 and V26 in sequence
+  - V23 → V26: Runs V24, V25, and V26 in sequence
+  - V20 → V26: Runs V21 through V26 in sequence
 
   ### Rollback Support
+  - V26 → V25: Removes user_file_checksum, renames file_checksum back to checksum, restores checksum unique index
+  - V25 → V24: Removes aspect ratio control from dimensions
   - V24 → V23: Removes unique index on checksum
   - V23 → V22: Removes session fingerprinting columns and indexes
   - V22 → V21: Removes audit logging system, email orphaned events, and email metrics
@@ -193,14 +212,14 @@ defmodule PhoenixKit.Migrations.Postgres do
 
   ## Usage Examples
 
-      # Update to latest version (V24)
+      # Update to latest version (V26)
       PhoenixKit.Migrations.Postgres.up(prefix: "myapp")
 
       # Update to specific version
-      PhoenixKit.Migrations.Postgres.up(prefix: "myapp", version: 24)
+      PhoenixKit.Migrations.Postgres.up(prefix: "myapp", version: 26)
 
       # Rollback to specific version
-      PhoenixKit.Migrations.Postgres.down(prefix: "myapp", version: 23)
+      PhoenixKit.Migrations.Postgres.down(prefix: "myapp", version: 25)
 
       # Complete rollback
       PhoenixKit.Migrations.Postgres.down(prefix: "myapp", version: 0)
@@ -218,7 +237,7 @@ defmodule PhoenixKit.Migrations.Postgres do
   use Ecto.Migration
 
   @initial_version 1
-  @current_version 25
+  @current_version 26
   @default_prefix "public"
 
   @doc false
diff --git a/lib/phoenix_kit/migrations/postgres/v26.ex b/lib/phoenix_kit/migrations/postgres/v26.ex
new file mode 100644
index 000000000..1b22fd631
--- /dev/null
+++ b/lib/phoenix_kit/migrations/postgres/v26.ex
@@ -0,0 +1,91 @@
+defmodule PhoenixKit.Migrations.Postgres.V26 do
+  @moduledoc """
+  Migration V26: Rename checksum fields and add per-user deduplication.
+
+  This migration renames checksum fields for clarity and adds per-user file deduplication
+  while preserving the ability to query for popular files across all users.
+
+  ## Changes
+  - Enables `pgcrypto` extension for cryptographic functions
+  - Renames `checksum` column to `file_checksum` (for clarity)
+  - Drops unique index on `file_checksum` (allows same file from different users)
+  - Adds `user_file_checksum` column (SHA256 of user_id + file_checksum)
+  - Creates unique index on `user_file_checksum` to enforce per-user uniqueness
+  - Backfills existing records with calculated user_file_checksum values
+
+  ## Requirements
+  - PostgreSQL with `pgcrypto` extension support (enabled automatically)
+
+  ## Purpose
+  - Same user cannot upload the same file twice (duplicate prevention via user_file_checksum)
+  - Different users CAN upload the same file (no unique constraint on file_checksum)
+  - Original `file_checksum` field preserved for finding most popular images across all users
+  - Clearer naming: file_checksum vs user_file_checksum
+  """
+
+  use Ecto.Migration
+
+  def up(%{prefix: prefix} = _opts) do
+    # Enable pgcrypto extension for digest function
+    execute "CREATE EXTENSION IF NOT EXISTS pgcrypto"
+
+    # Drop the unique index on checksum (from V24)
+    drop_if_exists unique_index(:phoenix_kit_files, [:checksum], prefix: prefix)
+
+    # Rename checksum to file_checksum for clarity
+    rename table(:phoenix_kit_files, prefix: prefix), :checksum, to: :file_checksum
+
+    # Add user_file_checksum column
+    alter table(:phoenix_kit_files, prefix: prefix) do
+      add :user_file_checksum, :string
+    end
+
+    # Backfill existing records with user_file_checksum
+    execute """
+    UPDATE #{prefix}.phoenix_kit_files
+    SET user_file_checksum = encode(digest(CAST(user_id AS text) || file_checksum, 'sha256'), 'hex')
+    WHERE user_file_checksum IS NULL
+    """
+
+    # Make the column NOT NULL after backfill
+    alter table(:phoenix_kit_files, prefix: prefix) do
+      modify :user_file_checksum, :string, null: false
+    end
+
+    # Create unique index on user_file_checksum for fast per-user duplicate detection
+    create unique_index(:phoenix_kit_files, [:user_file_checksum],
+             prefix: prefix,
+             name: "#{prefix}_phoenix_kit_files_user_file_checksum_index"
+           )
+
+    # Set version comment on phoenix_kit table for version tracking
+    execute "COMMENT ON TABLE #{prefix_table_name("phoenix_kit", prefix)} IS '26'"
+  end
+
+  def down(%{prefix: prefix} = _opts) do
+    # Drop the user_file_checksum unique index
+    drop_if_exists unique_index(:phoenix_kit_files, [:user_file_checksum],
+                     prefix: prefix,
+                     name: "#{prefix}_phoenix_kit_files_user_file_checksum_index"
+                   )
+
+    # Remove user_file_checksum column
+    alter table(:phoenix_kit_files, prefix: prefix) do
+      remove :user_file_checksum
+    end
+
+    # Rename file_checksum back to checksum
+    rename table(:phoenix_kit_files, prefix: prefix), :file_checksum, to: :checksum
+
+    # Restore the unique index on checksum (from V24)
+    create_if_not_exists unique_index(:phoenix_kit_files, [:checksum], prefix: prefix)
+
+    # Update version comment on phoenix_kit table to previous version
+    execute "COMMENT ON TABLE #{prefix_table_name("phoenix_kit", prefix)} IS '25'"
+  end
+
+  # Helper functions
+
+  defp prefix_table_name(table_name, nil), do: table_name
+  defp prefix_table_name(table_name, prefix), do: "#{prefix}.#{table_name}"
+end
diff --git a/lib/phoenix_kit/storage.ex b/lib/phoenix_kit/storage.ex
index 34183e5a5..6ecd379df 100644
--- a/lib/phoenix_kit/storage.ex
+++ b/lib/phoenix_kit/storage.ex
@@ -413,10 +413,41 @@ defmodule PhoenixKit.Storage do
   def get_file(id), do: repo().get(PhoenixKit.Storage.File, id)
 
   @doc """
-  Gets a file by its hash.
+  Calculates user-specific file checksum (salted with user_id).
+
+  This creates a unique checksum per user+file combination for duplicate detection,
+  while preserving the original file checksum for popularity queries.
+
+  ## Parameters
+    - user_id: The user ID (integer or string)
+    - file_checksum: The SHA256 checksum of the file content
+
+  ## Returns
+    String representing the SHA256 checksum of "user_id + file_checksum"
   """
-  def get_file_by_hash(hash) do
-    repo().get_by(PhoenixKit.Storage.File, checksum: hash)
+  def calculate_user_file_checksum(user_id, file_checksum) do
+    "#{user_id}#{file_checksum}"
+    |> then(fn data -> :crypto.hash(:sha256, data) end)
+    |> Base.encode16(case: :lower)
+  end
+
+  @doc """
+  Gets a file by its user-specific checksum.
+
+  This checks for duplicates for a specific user.
+  """
+  def get_file_by_user_checksum(user_file_checksum) do
+    repo().get_by(PhoenixKit.Storage.File, user_file_checksum: user_file_checksum)
+  end
+
+  @doc """
+  Gets a file by its original content checksum (file_checksum).
+
+  This can find files uploaded by any user with the same content.
+  Useful for popularity queries.
+  """
+  def get_file_by_checksum(file_checksum) do
+    repo().get_by(PhoenixKit.Storage.File, file_checksum: file_checksum)
   end
 
   @doc """
@@ -647,20 +678,24 @@ defmodule PhoenixKit.Storage do
 
     # Validate required fields
     if Elixir.File.exists?(source_path) do
-      # Calculate file hash
-      file_hash = calculate_file_hash(source_path)
+      # Calculate file checksum
+      file_checksum = calculate_file_hash(source_path)
 
-      # Check if file already exists
-      case get_file_by_hash(file_hash) do
+      # Calculate user-specific checksum for duplicate detection
+      user_file_checksum = calculate_user_file_checksum(user_id, file_checksum)
+
+      # Check if this user already uploaded this file
+      case get_file_by_user_checksum(user_file_checksum) do
         %PhoenixKit.Storage.File{} = existing_file ->
-          # File already exists, return existing file
+          # File already exists for this user, return existing file
           {:ok, existing_file}
 
         nil ->
-          # New file, proceed with storage
+          # New file for this user, proceed with storage
           store_new_file(
             source_path,
-            file_hash,
+            file_checksum,
+            user_file_checksum,
             filename,
             content_type,
             size_bytes,
@@ -706,7 +741,7 @@ defmodule PhoenixKit.Storage do
   Retrieves a file by its hash.
   """
   def retrieve_file_by_hash(hash) do
-    case get_file_by_hash(hash) do
+    case get_file_by_checksum(hash) do
       %PhoenixKit.Storage.File{} = file ->
         retrieve_file(file.id)
 
@@ -858,15 +893,18 @@ defmodule PhoenixKit.Storage do
         source_path,
         file_type,
         user_id,
-        file_hash,
+        file_checksum,
         ext,
         original_filename \\ nil
       ) do
-    # Check if file already exists by hash
-    case get_file_by_hash(file_hash) do
+    # Calculate user-specific hash for duplicate detection
+    user_file_checksum = calculate_user_file_checksum(user_id, file_checksum)
+
+    # Check if this user already uploaded this file
+    case get_file_by_user_checksum(user_file_checksum) do
       %PhoenixKit.Storage.File{} = existing_file ->
         Logger.info("=== DUPLICATE FILE DETECTED ===")
-        Logger.info("File ID: #{existing_file.id}, Checksum: #{file_hash}")
+        Logger.info("File ID: #{existing_file.id}, Checksum: #{file_checksum}")
         Logger.info("File path: #{existing_file.file_path}")
 
         # File already exists, but check if instances and actual files are healthy
@@ -892,7 +930,7 @@ defmodule PhoenixKit.Storage do
                 restore_missing_file(
                   existing_file,
                   source_path,
-                  file_hash,
+                  file_checksum,
                   user_id,
                   original_filename
                 )
@@ -910,7 +948,7 @@ defmodule PhoenixKit.Storage do
             recreate_file_instances(
               existing_file,
               source_path,
-              file_hash,
+              file_checksum,
               user_id,
               original_filename
             )
@@ -923,7 +961,8 @@ defmodule PhoenixKit.Storage do
           source_path,
           file_type,
           user_id,
-          file_hash,
+          file_checksum,
+          user_file_checksum,
           ext,
           original_filename
         )
@@ -934,7 +973,8 @@ defmodule PhoenixKit.Storage do
          source_path,
          file_type,
          user_id,
-         file_hash,
+         file_checksum,
+         user_file_checksum,
          ext,
          original_filename
        ) do
@@ -965,7 +1005,8 @@ defmodule PhoenixKit.Storage do
       mime_type: determine_mime_type(ext),
       file_type: file_type,
       ext: ext,
-      checksum: file_hash,
+      file_checksum: file_checksum,
+      user_file_checksum: user_file_checksum,
       size: get_file_size(source_path),
       status: "processing",
       user_id: user_id
@@ -984,7 +1025,7 @@ defmodule PhoenixKit.Storage do
               file_name: original_path,
               mime_type: file.mime_type,
               ext: ext,
-              checksum: file_hash,
+              checksum: file_checksum,
               size: get_file_size(source_path),
               processing_status: "completed",
               file_id: file.id
@@ -1067,7 +1108,7 @@ defmodule PhoenixKit.Storage do
     deleted_count
   end
 
-  defp recreate_file_instances(file, source_path, file_hash, user_id, original_filename) do
+  defp recreate_file_instances(file, source_path, file_checksum, user_id, original_filename) do
     # File record exists but instances are missing or broken
     # First store the file in buckets, then recreate the instance record
 
@@ -1103,7 +1144,7 @@ defmodule PhoenixKit.Storage do
           file_name: original_path,
           mime_type: file.mime_type,
           ext: file.ext,
-          checksum: file_hash,
+          checksum: file_checksum,
           size: file_size,
           processing_status: "completed",
           file_id: file.id
@@ -1260,7 +1301,8 @@ defmodule PhoenixKit.Storage do
 
   defp store_new_file(
          source_path,
-         file_hash,
+         file_checksum,
+         user_file_checksum,
          filename,
          content_type,
          size_bytes,
@@ -1275,7 +1317,8 @@ defmodule PhoenixKit.Storage do
             storage_info,
             filename,
             content_type,
-            file_hash,
+            file_checksum,
+            user_file_checksum,
             size_bytes,
             metadata,
             user_id
@@ -1284,7 +1327,7 @@ defmodule PhoenixKit.Storage do
         case create_file(file_attrs) do
           {:ok, file} ->
             # Create original instance and variants (non-critical operations)
-            create_original_instance_and_variants(file, file_hash, size_bytes)
+            create_original_instance_and_variants(file, file_checksum, size_bytes)
             {:ok, file}
 
           {:error, changeset} ->
@@ -1302,7 +1345,8 @@ defmodule PhoenixKit.Storage do
          storage_info,
          filename,
          content_type,
-         file_hash,
+         file_checksum,
+         user_file_checksum,
          size_bytes,
          metadata,
          user_id
@@ -1313,7 +1357,8 @@ defmodule PhoenixKit.Storage do
       mime_type: content_type,
       file_type: determine_file_type(content_type),
       ext: Path.extname(filename),
-      checksum: file_hash,
+      file_checksum: file_checksum,
+      user_file_checksum: user_file_checksum,
       size: size_bytes,
       # Convert to MB
       size_mb: size_bytes / (1024 * 1024),
@@ -1323,13 +1368,13 @@ defmodule PhoenixKit.Storage do
     }
   end
 
-  defp create_original_instance_and_variants(file, file_hash, size_bytes) do
+  defp create_original_instance_and_variants(file, file_checksum, size_bytes) do
     original_instance_attrs = %{
       variant_name: "original",
       file_name: file.file_name,
       mime_type: file.mime_type,
       ext: file.ext,
-      checksum: file_hash,
+      checksum: file_checksum,
       size: size_bytes,
       # Will be populated if we can detect dimensions
       width: nil,
diff --git a/lib/phoenix_kit/storage/file.ex b/lib/phoenix_kit/storage/file.ex
index e0bc88d9b..2c8c451ad 100644
--- a/lib/phoenix_kit/storage/file.ex
+++ b/lib/phoenix_kit/storage/file.ex
@@ -25,7 +25,8 @@ defmodule PhoenixKit.Storage.File do
   - `mime_type` - MIME type (image/jpeg, video/mp4, etc.)
   - `file_type` - High-level type (image, video, document, archive)
   - `ext` - File extension (jpg, mp4, pdf, etc.)
-  - `checksum` - MD5 or SHA256 hash for integrity verification
+  - `file_checksum` - SHA256 hash of file content for integrity verification
+  - `user_file_checksum` - SHA256 hash of (user_id + file_checksum) for per-user deduplication
   - `size` - File size in bytes
   - `width` - Image/video width in pixels (nullable)
   - `height` - Image/video height in pixels (nullable)
@@ -44,7 +45,8 @@ defmodule PhoenixKit.Storage.File do
         mime_type: "image/jpeg",
         file_type: "image",
         ext: "jpg",
-        checksum: "abc123def456...",
+        file_checksum: "abc123def456...",
+        user_file_checksum: "xyz789ghi012...",
         size: 524_288,  # 512 KB
         width: 2000,
         height: 2000,
@@ -60,6 +62,8 @@ defmodule PhoenixKit.Storage.File do
         mime_type: "video/mp4",
         file_type: "video",
         ext: "mp4",
+        file_checksum: "def456ghi789...",
+        user_file_checksum: "mno345pqr678...",
         size: 10_485_760,  # 10 MB
         width: 1920,
         height: 1080,
@@ -75,6 +79,8 @@ defmodule PhoenixKit.Storage.File do
         mime_type: "application/pdf",
         file_type: "document",
         ext: "pdf",
+        file_checksum: "ghi789jkl012...",
+        user_file_checksum: "stu901vwx234...",
         size: 2_097_152,  # 2 MB
         status: "active"
       }
@@ -93,7 +99,8 @@ defmodule PhoenixKit.Storage.File do
           mime_type: String.t(),
           file_type: String.t(),
           ext: String.t(),
-          checksum: String.t(),
+          file_checksum: String.t(),
+          user_file_checksum: String.t(),
           size: integer(),
           width: integer() | nil,
           height: integer() | nil,
@@ -114,7 +121,8 @@ defmodule PhoenixKit.Storage.File do
     field :mime_type, :string
     field :file_type, :string
     field :ext, :string
-    field :checksum, :string
+    field :file_checksum, :string
+    field :user_file_checksum, :string
     field :size, :integer
     field :width, :integer
     field :height, :integer
@@ -138,7 +146,8 @@ defmodule PhoenixKit.Storage.File do
   - `mime_type`
   - `file_type` (must be: "image", "video", "document", "archive")
   - `ext`
-  - `checksum`
+  - `file_checksum`
+  - `user_file_checksum`
   - `size`
   - `user_id`
 
@@ -159,7 +168,8 @@ defmodule PhoenixKit.Storage.File do
       :mime_type,
       :file_type,
       :ext,
-      :checksum,
+      :file_checksum,
+      :user_file_checksum,
       :size,
       :width,
       :height,
@@ -174,7 +184,8 @@ defmodule PhoenixKit.Storage.File do
       :mime_type,
       :file_type,
       :ext,
-      :checksum,
+      :file_checksum,
+      :user_file_checksum,
       :size,
       :user_id
     ])
diff --git a/lib/phoenix_kit_web/controllers/upload_controller.ex b/lib/phoenix_kit_web/controllers/upload_controller.ex
index ce5608f9d..41d64a801 100644
--- a/lib/phoenix_kit_web/controllers/upload_controller.ex
+++ b/lib/phoenix_kit_web/controllers/upload_controller.ex
@@ -150,19 +150,22 @@ defmodule PhoenixKitWeb.UploadController do
 
   defp process_upload(upload, user_id) do
     with {:ok, stat} <- File.stat(upload.path),
-         {:ok, file_hash} <- safe_calculate_file_hash(upload.path) do
+         {:ok, file_checksum} <- safe_calculate_file_hash(upload.path) do
       file_size = stat.size
 
-      # Check if file already exists
-      case Storage.get_file_by_hash(file_hash) do
+      # Calculate user-specific checksum for per-user duplicate detection
+      user_file_checksum = Storage.calculate_user_file_checksum(user_id, file_checksum)
+
+      # Check if this user already uploaded this file
+      case Storage.get_file_by_user_checksum(user_file_checksum) do
         %StorageFile{} = existing_file ->
-          # File already exists, delete temp upload and return existing file
+          # File already exists for this user, delete temp upload and return existing file
           File.rm(upload.path)
           {:ok, existing_file.id}
 
         nil ->
-          # New file, proceed with upload
-          perform_upload(upload, user_id, file_size, file_hash)
+          # New file for this user, proceed with upload
+          perform_upload(upload, user_id, file_size, file_checksum)
       end
     else
       {:error, reason} -> {:error, reason}
@@ -184,12 +187,12 @@ defmodule PhoenixKitWeb.UploadController do
     end
   end
 
-  defp perform_upload(upload, user_id, _file_size, file_hash) do
+  defp perform_upload(upload, user_id, _file_size, file_checksum) do
     file_type = determine_file_type(upload.content_type)
     ext = Path.extname(upload.filename) |> String.replace_leading(".", "")
 
     # Store in buckets with hierarchical path structure
-    case Storage.store_file_in_buckets(upload.path, file_type, user_id, file_hash, ext) do
+    case Storage.store_file_in_buckets(upload.path, file_type, user_id, file_checksum, ext) do
       {:ok, file} ->
         # Queue background job for variant generation
         %{file_id: file.id, user_id: user_id, filename: upload.filename}