diff --git a/core/src/databases/database.rs b/core/src/databases/database.rs
index 7849c750629c..3b6d19a773ff 100644
--- a/core/src/databases/database.rs
+++ b/core/src/databases/database.rs
@@ -224,15 +224,39 @@ impl Table {
         rows: &Vec<Row>,
         truncate: bool,
     ) -> Result<()> {
-        // Validate the tables schema, merge it if necessary and store it in the schema cache.
-        let table_schema = match self.schema() {
-            // If there is no existing schema cache, simply use the new schema.
-            None => TableSchema::from_rows(&rows)?,
-            Some(existing_table_schema) => {
-                // If there is an existing schema cache, merge it with the new schema.
-                existing_table_schema.merge(&TableSchema::from_rows(&rows)?)?
+        // Validate that all rows keys are lowercase.
+        for (row_index, row) in rows.iter().enumerate() {
+            let object = match row.value().as_object() {
+                Some(object) => object,
+                None => Err(anyhow!("Row {} is not an object", row_index,))?,
+            };
+            match object.keys().find(|key| match key.chars().next() {
+                Some(c) => !c.is_ascii_lowercase(),
+                None => false,
+            }) {
+                Some(key) => Err(anyhow!(
+                    "Row {} has a key '{}' that is not lowercase",
+                    row_index,
+                    key
+                ))?,
+                None => (),
             }
+        }
+
+        // Validate the tables schema, merge it if necessary and store it in the schema cache.
+        let table_schema = match truncate {
+            // If the new rows replace existing ones, we need to clear the schema cache.
+            true => TableSchema::from_rows(&rows)?,
+            false => match self.schema() {
+                // If there is no existing schema cache, simply use the new schema.
+                None => TableSchema::from_rows(&rows)?,
+                Some(existing_table_schema) => {
+                    // If there is an existing schema cache, merge it with the new schema.
+                    existing_table_schema.merge(&TableSchema::from_rows(&rows)?)?
+                }
+            },
         };
+
         store
             .update_table_schema(
                 &self.project,
diff --git a/front/pages/api/v1/w/[wId]/data_sources/[name]/tables/[tId]/rows/index.ts b/front/pages/api/v1/w/[wId]/data_sources/[name]/tables/[tId]/rows/index.ts
index 8dee81e6e5d7..352db1a9bde2 100644
--- a/front/pages/api/v1/w/[wId]/data_sources/[name]/tables/[tId]/rows/index.ts
+++ b/front/pages/api/v1/w/[wId]/data_sources/[name]/tables/[tId]/rows/index.ts
@@ -151,8 +151,31 @@ async function handler(
           status_code: 400,
         });
       }
-      const { rows: rowsToUpsert, truncate } = bodyValidation.right;
-
+      const { truncate } = bodyValidation.right;
+      let { rows: rowsToUpsert } = bodyValidation.right;
+
+      // Make every key in the rows lowercase and ensure there are no duplicates.
+      const allKeys = rowsToUpsert.map((row) => Object.keys(row.value)).flat();
+      const keysSet = new Set<string>();
+      for (const key of allKeys) {
+        if (keysSet.has(key)) {
+          return apiError(req, res, {
+            status_code: 400,
+            api_error: {
+              type: "invalid_request_error",
+              message: `Duplicate key: ${key}`,
+            },
+          });
+        }
+        keysSet.add(key);
+      }
+      rowsToUpsert = rowsToUpsert.map((row) => {
+        const value: Record<string, string | number | boolean | null> = {};
+        for (const [key, val] of Object.entries(row.value)) {
+          value[key.toLowerCase()] = val;
+        }
+        return { row_id: row.row_id, value };
+      });
       const upsertRes = await coreAPI.upsertTableRows({
         projectId: dataSource.dustAPIProjectId,
         dataSourceName: dataSource.name,
diff --git a/front/pages/api/w/[wId]/data_sources/[name]/tables/csv.ts b/front/pages/api/w/[wId]/data_sources/[name]/tables/csv.ts
index 9f2999aa801a..7039dd283393 100644
--- a/front/pages/api/w/[wId]/data_sources/[name]/tables/csv.ts
+++ b/front/pages/api/w/[wId]/data_sources/[name]/tables/csv.ts
@@ -258,6 +258,18 @@ async function rowsFromCsv(
       continue;
     }
 
+    header = header.map((h) => h.trim().toLowerCase());
+    const headerSet = new Set<string>();
+    for (const h of header) {
+      if (headerSet.has(h)) {
+        return new Err({
+          type: "invalid_request_error",
+          message: `Duplicate header: ${h}.`,
+        });
+      }
+      headerSet.add(h);
+    }
+
     for (const [i, h] of header.entries()) {
       const col = record[i];
       if (col === undefined) {