diff --git a/cmd/main.go b/cmd/main.go
index 6291cf2c..63dbf849 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -4,7 +4,7 @@ import (
 	"bufio"
 	"flag"
 	"fmt"
-	"log"
+	"log/slog"
 	"os"
 	"time"
 
@@ -12,16 +12,24 @@ import (
 )
 
 func main() {
+	var debugFlag, jsonlFlag, csvFlag, showTimings bool
 
-	var jsonlFlag bool
-	var csvFlag bool
-
+	flag.BoolVar(&debugFlag, "debug", false, "Use logger that prints at the debug-level")
 	flag.BoolVar(&jsonlFlag, "jsonl", false, "Use JSONL handler")
 	flag.BoolVar(&csvFlag, "csv", false, "Use CSV handler")
-
-	var showTimings bool
 	flag.BoolVar(&showTimings, "t", false, "Show time-related metrics")
 
+	flag.Parse()
+
+	logLevel := &slog.LevelVar{}
+
+	if debugFlag {
+		logLevel.Set(slog.LevelDebug)
+	}
+
+	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: logLevel}))
+	slog.SetDefault(logger)
+
 	var totalStart, readStart, writeStart time.Time
 	if showTimings {
 		totalStart = time.Now()
@@ -33,7 +41,6 @@ func main() {
 		flag.PrintDefaults()
 		os.Exit(1)
 	}
-	flag.Parse()
 
 	args := flag.Args()
 
@@ -47,32 +54,34 @@ func main() {
 		panic(err)
 	}
 
-
 	var dataHandler appendable.DataHandler
 
 	switch {
 	case jsonlFlag:
-		dataHandler = appendable.JSONLHandler{ReadSeeker: file}
+		dataHandler = appendable.JSONLHandler{
+			ReadSeeker: file,
+		}
 	case csvFlag:
-		dataHandler = appendable.CSVHandler{ReadSeeker: file}
+		dataHandler = appendable.CSVHandler{
+			ReadSeeker: file,
+		}
 	default:
-		fmt.Println("Please specify the file type with -jsonl or -csv.")
+		logger.Error("Please specify the file type with -jsonl or -csv.")
 		os.Exit(1)
 	}
-  if showTimings {
+	if showTimings {
 		readStart = time.Now()
 	}
 	// Open the index file
 	indexFile, err := appendable.NewIndexFile(dataHandler)
 
+	if err != nil {
+		panic(err)
+	}
 
 	if showTimings {
 		readDuration := time.Since(readStart)
-		log.Printf("Opening + synchronizing index file took: %s", readDuration)
-	}
-
-	if err != nil {
-		panic(err)
+		logger.Info("Opening + synchronizing index file took", slog.Duration("duration", readDuration))
 	}
 
 	// Write the index file
@@ -83,7 +92,7 @@ func main() {
 	if err != nil {
 		panic(err)
 	}
-	log.Printf("Writing index file to %s", args[0]+".index")
+	logger.Info("Writing index file to", slog.String("path", args[0]+".index"))
 	bufof := bufio.NewWriter(of)
 	if err := indexFile.Serialize(bufof); err != nil {
 		panic(err)
@@ -97,11 +106,11 @@ func main() {
 
 	if showTimings {
 		writeDuration := time.Since(writeStart)
-		log.Printf("Writing index file took: %s", writeDuration)
+		logger.Info("Writing index file took", slog.Duration("duration", writeDuration))
 
 		totalDuration := time.Since(totalStart)
-		log.Printf("Total execution time: %s", totalDuration)
+		logger.Info("Total execution time", slog.Duration("duration", totalDuration))
 	}
 
-	log.Printf("Done!")
+	logger.Info("Done!")
 }
diff --git a/pkg/appendable/csv_handler.go b/pkg/appendable/csv_handler.go
index 3d3c69fb..c3d00519 100644
--- a/pkg/appendable/csv_handler.go
+++ b/pkg/appendable/csv_handler.go
@@ -6,6 +6,7 @@ import (
 	"encoding/csv"
 	"fmt"
 	"io"
+	"log/slog"
 	"strconv"
 	"strings"
 
@@ -18,6 +19,8 @@ type CSVHandler struct {
 }
 
 func (c CSVHandler) Synchronize(f *IndexFile) error {
+	slog.Debug("Starting CSV synchronization")
+
 	var headers []string
 	var err error
 
@@ -52,9 +55,11 @@ func (c CSVHandler) Synchronize(f *IndexFile) error {
 		f.Checksums = append(f.Checksums, xxhash.Sum64(line))
 
 		if isHeader {
+			slog.Info("Parsing CSV headers")
 			dec := csv.NewReader(bytes.NewReader(line))
 			headers, err = dec.Read()
 			if err != nil {
+				slog.Error("failed to parse CSV header", "error", err)
 				return fmt.Errorf("failed to parse CSV header: %w", err)
 			}
 			isHeader = false
@@ -62,14 +67,19 @@ func (c CSVHandler) Synchronize(f *IndexFile) error {
 		}
 
 		dec := csv.NewReader(bytes.NewReader(line))
+		slog.Debug("Handling csv", "line", i)
 		f.handleCSVLine(dec, headers, []string{}, uint64(existingCount)-1, start)
+		slog.Info("Succesfully processed", "line", i)
 	}
 
 	if fromNewIndexFile && len(f.EndByteOffsets) > 0 {
 		f.EndByteOffsets = f.EndByteOffsets[1:]
 		f.Checksums = f.Checksums[1:]
+
+		slog.Debug("Trimming endbyte offsets and checksums", "endByteOffsets", slog.Any("endByteOffsets", f.EndByteOffsets), "checksums", slog.Any("checksums", f.Checksums))
 	}
 
+	slog.Debug("Ending CSV synchronization")
 	return nil
 }
 
@@ -89,7 +99,6 @@ func fieldRankCsvField(fieldValue any) int {
 }
 
 func inferCSVField(fieldValue string) (interface{}, protocol.FieldType) {
-
 	if fieldValue == "" {
 		return nil, protocol.FieldTypeNull
 	}
@@ -110,17 +119,22 @@ func inferCSVField(fieldValue string) (interface{}, protocol.FieldType) {
 }
 
 func (i *IndexFile) handleCSVLine(dec *csv.Reader, headers []string, path []string, dataIndex, dataOffset uint64) error {
+	slog.Debug("Processing CSV line", slog.Int("dataIndex", int(dataIndex)), slog.Int("dataOffset", int(dataOffset)))
 
 	record, err := dec.Read()
 
 	if err != nil {
+		slog.Error("Failed to read CSV record at index", "dataIndex", dataIndex, "error", err)
 		return fmt.Errorf("failed to read CSV record at index %d: %w", dataIndex, err)
 	}
 
+	slog.Debug("CSV line read successfully", "record", record)
+
 	cumulativeLength := uint64(0)
 
 	for fieldIndex, fieldValue := range record {
 		if fieldIndex >= len(headers) {
+			slog.Error("Field index is out of bounds with headers", "fieldIndex", fieldIndex, "headers", slog.Any("headers", headers))
 			return fmt.Errorf("field index %d is out of bounds with header", fieldIndex)
 		}
 
@@ -142,14 +156,21 @@ func (i *IndexFile) handleCSVLine(dec *csv.Reader, headers []string, path []stri
 				FieldLength:          int(fieldLength),
 			})
 
+			slog.Debug("Appended index record",
+				slog.String("field", name),
+				slog.Any("value", value),
+				slog.Int("start", int(fieldOffset)))
+
 		case protocol.FieldTypeNull:
 			for j := range i.Indexes {
 				if i.Indexes[j].FieldName == name {
 					i.Indexes[j].FieldType |= protocol.FieldTypeNull
 				}
 			}
+			slog.Debug("Marked field", "name", name)
 
 		default:
+			slog.Error("Encountered unexpected type '%T' for field '%s'", value, name)
 			return fmt.Errorf("unexpected type '%T'", value)
 		}
 
diff --git a/pkg/appendable/index_file_jsonl_test.go b/pkg/appendable/index_file_jsonl_test.go
index 19f8afa5..cd015a69 100644
--- a/pkg/appendable/index_file_jsonl_test.go
+++ b/pkg/appendable/index_file_jsonl_test.go
@@ -9,6 +9,7 @@ import (
 )
 
 func TestAppendDataRowJSONL(t *testing.T) {
+
 	t.Run("no schema changes", func(t *testing.T) {
 
 		i, err := NewIndexFile(JSONLHandler{ReadSeeker: strings.NewReader("{\"test\":\"test1\"}\n")})
diff --git a/pkg/appendable/index_file_test.go b/pkg/appendable/index_file_test.go
index 900956e7..d339e5da 100644
--- a/pkg/appendable/index_file_test.go
+++ b/pkg/appendable/index_file_test.go
@@ -2,6 +2,8 @@ package appendable
 
 import (
 	"fmt"
+	"log/slog"
+	"os"
 	"strings"
 	"testing"
 
@@ -21,10 +23,22 @@ jsonl <---> csv
 */
 func TestIndexFile(t *testing.T) {
 
+	originalLogger := slog.Default()
+
+	// Create a logger with Debug on
+	debugLevel := &slog.LevelVar{}
+	debugLevel.Set(slog.LevelDebug)
+	debugLogger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
+		Level: debugLevel,
+	}))
+
+	slog.SetDefault(debugLogger)
+
+	defer slog.SetDefault(originalLogger)
+
 	mockJsonl := "{\"id\":\"identification\", \"age\":\"cottoneyedjoe\"}\n"
 	mockCsv := "id,age\nidentification,cottoneyedjoe\n"
 
-
 	t.Run("generate index file", func(t *testing.T) {
 		// jsonl
 		jif, err := NewIndexFile(JSONLHandler{ReadSeeker: strings.NewReader(mockJsonl)})
@@ -40,7 +54,7 @@ func TestIndexFile(t *testing.T) {
 		}
 
 		status, res := jif.compareTo(civ)
-    
+
 		if !status {
 			t.Errorf("Not equal\n%v", res)
 		}
@@ -49,21 +63,28 @@ func TestIndexFile(t *testing.T) {
 
 }
 
-func compareIndexRecord(ir1, ir2 *protocol.IndexRecord) (bool, string) {
+func compareIndexRecord(ir1, ir2 *protocol.IndexRecord, fieldType protocol.FieldType) (bool, string) {
 	if ir1.DataNumber != ir2.DataNumber {
 		return false, fmt.Sprintf("Index record data numbers do not align\ti1: %v, i2: %v", ir1.DataNumber, ir2.DataNumber)
 	}
 
-	/*
-			if ir1.FieldStartByteOffset != ir2.FieldStartByteOffset {
-				return false, fmt.Sprintf("FieldStartByteOffset do not align\ti1: %v, i2: %v", ir1.FieldStartByteOffset, ir2.FieldStartByteOffset)
-			}
+	if fieldType&protocol.FieldTypeString != protocol.FieldTypeString {
+		if ir1.FieldStartByteOffset != ir2.FieldStartByteOffset {
+			return false, fmt.Sprintf("FieldStartByteOffset do not align\ti1: %v, i2: %v", ir1.FieldStartByteOffset, ir2.FieldStartByteOffset)
+		}
 
 		if ir1.FieldLength != ir2.FieldLength {
 			return false, fmt.Sprintf("Field Length do not align\ti1: %v, i2: %v", ir1.FieldLength, ir2.FieldLength)
 		}
+	} /* else {
+		if ir1.FieldStartByteOffset != ir2.FieldStartByteOffset {
+			return false, fmt.Sprintf("FieldStartByteOffset do not align\ti1: %v, i2: %v", ir1.FieldStartByteOffset, ir2.FieldStartByteOffset)
+		}
 
-	*/
+		if ir1.FieldLength != ir2.FieldLength {
+			return false, fmt.Sprintf("Field Length do not align\ti1: %v, i2: %v", ir1.FieldLength, ir2.FieldLength)
+		}
+	}*/
 	return true, ""
 }
 
@@ -90,7 +111,7 @@ func (i1 *Index) compareIndex(i2 *Index) (bool, string) {
 		}
 
 		for i := range records1 {
-			status, res := compareIndexRecord(&records1[i], &records2[i])
+			status, res := compareIndexRecord(&records1[i], &records2[i], i1.FieldType)
 			if !status {
 				return false, res
 			}
@@ -123,16 +144,15 @@ func (i1 *IndexFile) compareTo(i2 *IndexFile) (bool, string) {
 	if len(i1.EndByteOffsets) != len(i2.EndByteOffsets) {
 		return false, fmt.Sprintf("endbyteoffsets length not equal\ti1: %v, i2: %v", len(i1.EndByteOffsets), len(i2.EndByteOffsets))
 	}
-  
+
 	fmt.Printf("endbyteoffsets equal")
 
 	if len(i1.Checksums) != len(i2.Checksums) {
 		return false, fmt.Sprintf("checksums length not equal\ti1: %v, i2: %v", len(i1.Checksums), len(i2.Checksums))
 	}
 
-
 	fmt.Printf("checksums equal")
-  
+
 	/*
 		for i, _ := range i1.EndByteOffsets {
 			if i1.EndByteOffsets[i] != i2.EndByteOffsets[i] {
diff --git a/pkg/appendable/io_test.go b/pkg/appendable/io_test.go
index cfa733b2..bf71b2ca 100644
--- a/pkg/appendable/io_test.go
+++ b/pkg/appendable/io_test.go
@@ -8,6 +8,7 @@ import (
 )
 
 func TestReadIndexFile(t *testing.T) {
+
 	t.Run("empty index file", func(t *testing.T) {
 		if _, err := ReadIndexFile(strings.NewReader(""), JSONLHandler{ReadSeeker: strings.NewReader("")}); !errors.Is(err, io.EOF) {
 			t.Errorf("expected EOF, got %v", err)