diff --git a/README.md b/README.md
index 29311d5..d6c96de 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ defer testTxt.Close()
 
 s3 := simples3.New(Region, AWSAccessKey, AWSSecretKey)
 err := s3.FileUpload(simples3.UploadInput{
-    Bucket:      "zerodha-testbucket",
+    Bucket:      AWSBucket,
     ObjectKey:   "test.txt",
     ContentType: "text/plain",
     FileName:    "test.txt",
diff --git a/policy.go b/policy.go
index 4d62bb7..aaa8ec6 100644
--- a/policy.go
+++ b/policy.go
@@ -51,6 +51,7 @@ const (
 	serviceName              = "s3"
 
 	defaultUploadURLFormat = "http://%s.s3.amazonaws.com/" // <bucketName>
+	defaultBucketURLFormat = "%s.s3.amazonaws.com/"        // <bucketName>
 	defaultExpirationHour  = 1 * time.Hour
 )
 
@@ -130,6 +131,10 @@ func (s3 S3) buildCredential(nowTime time.Time) string {
 	return fmt.Sprintf("%s/%s/%s/%s/%s", s3.AccessKey, nowTime.UTC().Format(shortTimeFormat), s3.Region, serviceName, "aws4_request")
 }
 
+func (s3 S3) buildCredentialWithoutKey(nowTime time.Time) string {
+	return fmt.Sprintf("%s/%s/%s/%s", nowTime.UTC().Format(shortTimeFormat), s3.Region, serviceName, "aws4_request")
+}
+
 func buildSignature(nowTime time.Time, secretAccessKey string, regionName string, serviceName string) []byte {
 	shortTime := nowTime.UTC().Format(shortTimeFormat)
 
diff --git a/presigned.go b/presigned.go
new file mode 100644
index 0000000..0406864
--- /dev/null
+++ b/presigned.go
@@ -0,0 +1,162 @@
+package simples3
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"net/url"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+const (
+	defaultPresignedURLFormat = "%s.s3.amazonaws.com" // <bucket>
+)
+
+type PresignedInput struct {
+	Bucket        string
+	ObjectKey     string
+	Method        string
+	Timestamp     time.Time
+	ExtraHeaders  map[string]string
+	ExpirySeconds int
+}
+
+func (s3 *S3) GeneratePresignedURL(in PresignedInput) string {
+	var (
+		nowTime = in.Timestamp.UTC()
+		cred    = s3.buildCredential(nowTime)
+		amzdate = nowTime.Format(amzDateISO8601TimeFormat)
+		expiry  = strconv.Itoa(in.ExpirySeconds)
+	)
+
+	// Add host to Headers
+	signedHeaders := in.ExtraHeaders
+	if signedHeaders == nil {
+		signedHeaders = map[string]string{}
+	}
+	signedHeaders["host"] = fmt.Sprintf(defaultPresignedURLFormat, in.Bucket)
+
+	// Start Canonical Request Formation
+	h := sha256.New()
+	fmt.Fprintf(h, "%s\n", in.Method)     // HTTP Verb
+	fmt.Fprintf(h, "/%s\n", in.ObjectKey) // CanonicalURL
+
+	// Start QueryString Params (before SignedHeaders)
+	queryString := map[string]string{
+		"X-Amz-Algorithm":  algorithm,
+		"X-Amz-Credential": cred,
+		"X-Amz-Date":       amzdate,
+		"X-Amz-Expires":    expiry,
+	}
+
+	// We need to have a sorted order,
+	keysQS := make([]string, 0, len(queryString))
+	for name := range queryString {
+		keysQS = append(keysQS, name)
+	}
+	sort.Strings(keysQS) //sort by key
+	for _, k := range keysQS {
+		fmt.Fprintf(h, "%s=%s&", url.QueryEscape(k), url.QueryEscape(queryString[k])) // HTTP Verb
+	}
+
+	fmt.Fprintf(h, "X-Amz-SignedHeaders=")
+	// Add Signed Headers to Query String
+	first := true
+	for k := range signedHeaders {
+		if first {
+			fmt.Fprintf(h, "%s", url.QueryEscape(k))
+			first = false
+		} else {
+			fmt.Fprintf(h, "%s", url.QueryEscape(";"+k))
+		}
+	}
+	fmt.Fprintf(h, "\n")
+	// End QueryString Params
+
+	// Start Canonical Headers
+	for k, v := range signedHeaders {
+		fmt.Fprintf(h, "%s:%s\n", strings.ToLower(k), strings.TrimSpace(v))
+	}
+	fmt.Fprintf(h, "\n")
+	// End Canonical Headers
+
+	// Start Signed Headers
+	first = true
+	for k := range signedHeaders {
+		if first {
+			fmt.Fprintf(h, "%s", url.QueryEscape(k))
+			first = false
+		} else {
+			fmt.Fprintf(h, "%s", url.QueryEscape(";"+k))
+		}
+	}
+	fmt.Fprintf(h, "\n")
+	// End Canonical Headers
+
+	// Mention Unsigned Payload
+	fmt.Fprintf(h, "UNSIGNED-PAYLOAD")
+
+	// canonicalReq := h.Bytes()
+	// Reset Buffer to create StringToSign
+	var b bytes.Buffer
+
+	// Start StringToSign
+	fmt.Fprintf(&b, "%s\n", algorithm)                             // Algo
+	fmt.Fprintf(&b, "%s\n", amzdate)                               // Date
+	fmt.Fprintf(&b, "%s\n", s3.buildCredentialWithoutKey(nowTime)) //Cred
+
+	hashed := hex.EncodeToString(h.Sum(nil))
+	fmt.Fprintf(&b, "%s", hashed)
+
+	stringToSign := b.Bytes()
+
+	// End StringToSign
+
+	// Start Signature Key
+	sigKey := makeHMac(makeHMac(
+		makeHMac(
+			makeHMac(
+				[]byte("AWS4"+s3.SecretKey),
+				[]byte(nowTime.UTC().Format(shortTimeFormat))),
+			[]byte(s3.Region)),
+		[]byte("s3")),
+		[]byte("aws4_request"),
+	)
+	// sigKey gen verified using https://docs.aws.amazon.com/general/latest/gr/signature-v4-examples.html#signature-v4-examples-other
+	// (TODO: add a test using the same, consolidate with signKeys())
+
+	signedStrToSign := makeHMac(sigKey, stringToSign)
+	signature := hex.EncodeToString(signedStrToSign)
+	// End Signature
+
+	// Reset Buffer to create URl
+	b.Reset()
+
+	// Start Generating URL
+	fmt.Fprintf(&b, "http://"+defaultPresignedURLFormat+"/", in.Bucket)
+	fmt.Fprintf(&b, "%s?", in.ObjectKey)
+
+	// We don't need to have a sorted order here,
+	// but just to preserve tests.
+	for _, k := range keysQS {
+		fmt.Fprintf(&b, "%s=%s&", url.QueryEscape(k), url.QueryEscape(queryString[k])) // HTTP Verb
+	}
+	fmt.Fprintf(&b, "%s=", "X-Amz-SignedHeaders")
+	first = true
+	for k := range signedHeaders {
+		if first {
+			fmt.Fprintf(&b, "%s", url.QueryEscape(k))
+			first = false
+		} else {
+			fmt.Fprintf(&b, "%s", url.QueryEscape(";"+k))
+		}
+	}
+	fmt.Fprintf(&b, "&X-Amz-Signature=%s", signature)
+	resultURL := b.String()
+
+	return resultURL
+}
diff --git a/presigned_test.go b/presigned_test.go
new file mode 100644
index 0000000..dd04c2c
--- /dev/null
+++ b/presigned_test.go
@@ -0,0 +1,70 @@
+package simples3
+
+import (
+	"os"
+	"testing"
+	"time"
+)
+
+func TestS3_GeneratePresignedURL(t *testing.T) {
+	// Params based on
+	// https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html
+	var time, _ = time.Parse(time.RFC1123, "Fri, 24 May 2013 00:00:00 GMT")
+	t.Run("Test", func(t *testing.T) {
+		s := New(
+			"us-east-1",
+			"AKIAIOSFODNN7EXAMPLE",
+			"wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
+		)
+		want := "http://examplebucket.s3.amazonaws.com/test.txt?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIOSFODNN7EXAMPLE%2F20130524%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20130524T000000Z&X-Amz-Expires=86400&X-Amz-SignedHeaders=host&X-Amz-Signature=aeeed9bbccd4d02ee5c0109b86d86835f995330da4c265957d157751f604d404"
+		if got := s.GeneratePresignedURL(PresignedInput{
+			Bucket:        "examplebucket",
+			ObjectKey:     "test.txt",
+			Method:        "GET",
+			Timestamp:     time,
+			ExpirySeconds: 86400,
+		}); got != want {
+			t.Errorf("S3.GeneratePresignedURL() = %v, want %v", got, want)
+		}
+	})
+}
+
+func TestS3_GeneratePresignedURL_Personal(t *testing.T) {
+	t.Run("Test", func(t *testing.T) {
+		s := New(
+			os.Getenv("AWS_S3_REGION"),
+			os.Getenv("AWS_S3_ACCESS_KEY"),
+			os.Getenv("AWS_S3_SECRET_KEY"),
+		)
+		dontwant := ""
+		if got := s.GeneratePresignedURL(PresignedInput{
+			Bucket:        os.Getenv("AWS_S3_BUCKET"),
+			ObjectKey:     "test1.txt",
+			Method:        "GET",
+			Timestamp:     NowTime(),
+			ExpirySeconds: 3600,
+		}); got == dontwant {
+			t.Errorf("S3.GeneratePresignedURL() = %v, dontwant %v", got, dontwant)
+		}
+	})
+}
+
+func TestS3_GeneratePresignedURL_POST(t *testing.T) {
+	t.Run("Test", func(t *testing.T) {
+		s := New(
+			os.Getenv("AWS_S3_REGION"),
+			os.Getenv("AWS_S3_ACCESS_KEY"),
+			os.Getenv("AWS_S3_SECRET_KEY"),
+		)
+		dontwant := ""
+		if got := s.GeneratePresignedURL(PresignedInput{
+			Bucket:        os.Getenv("AWS_S3_BUCKET"),
+			ObjectKey:     "test2.txt",
+			Method:        "PUT",
+			Timestamp:     NowTime(),
+			ExpirySeconds: 3600,
+		}); got == dontwant {
+			t.Errorf("S3.GeneratePresignedURL() = %v, dontwant %v", got, dontwant)
+		}
+	})
+}
diff --git a/sign.go b/sign.go
index e5faf34..9e88e31 100644
--- a/sign.go
+++ b/sign.go
@@ -45,7 +45,7 @@ func (s3 *S3) writeRequest(w io.Writer, r *http.Request) {
 }
 
 func (s3 *S3) writeStringToSign(w io.Writer, t time.Time, r *http.Request) {
-	w.Write([]byte("AWS4-HMAC-SHA256"))
+	w.Write([]byte(algorithm))
 	w.Write(newLine)
 	w.Write([]byte(t.Format(amzDateISO8601TimeFormat)))
 	w.Write(newLine)
diff --git a/simples3.go b/simples3.go
index ff025d0..a19e7c9 100644
--- a/simples3.go
+++ b/simples3.go
@@ -170,7 +170,7 @@ func (s3 *S3) FileDelete(u DeleteInput) error {
 
 	s3.writeStringToSign(h, t, req)
 
-	auth := bytes.NewBufferString("AWS4-HMAC-SHA256 ")
+	auth := bytes.NewBufferString(algorithm)
 	auth.Write([]byte("Credential=" + s3.AccessKey + "/" + s3.creds(t)))
 	auth.Write([]byte{',', ' '})
 	auth.Write([]byte("SignedHeaders="))
diff --git a/simples3_test.go b/simples3_test.go
index 8d362de..8cbcc38 100644
--- a/simples3_test.go
+++ b/simples3_test.go
@@ -35,7 +35,7 @@ func TestS3_FileUpload(t *testing.T) {
 			},
 			args: args{
 				UploadInput{
-					Bucket:      "zerodha-testbucket",
+					Bucket:      os.Getenv("AWS_S3_BUCKET"),
 					ObjectKey:   "test.txt",
 					ContentType: "text/plain",
 					FileName:    "test.txt",
@@ -79,7 +79,7 @@ func TestS3_FileDelete(t *testing.T) {
 			},
 			args: args{
 				DeleteInput{
-					Bucket:    "zerodha-testbucket",
+					Bucket:    os.Getenv("AWS_S3_BUCKET"),
 					ObjectKey: "test.txt",
 				},
 			},