diff --git a/actix-http/Cargo.toml b/actix-http/Cargo.toml
index cd813e49f..d27bca7e7 100644
--- a/actix-http/Cargo.toml
+++ b/actix-http/Cargo.toml
@@ -93,8 +93,13 @@ actix-server = "1.0.0"
 actix-connect = { version = "1.0.0", features=["openssl"] }
 actix-http-test = { version = "1.0.0", features=["openssl"] }
 actix-tls = { version = "1.0.0", features=["openssl"] }
+criterion = "0.3"
 futures = "0.3.1"
 env_logger = "0.6"
 serde_derive = "1.0"
 open-ssl = { version="0.10", package = "openssl" }
 rust-tls = { version="0.16", package = "rustls" }
+
+[[bench]]
+name = "content-length"
+harness = false
diff --git a/actix-http/benches/content-length.rs b/actix-http/benches/content-length.rs
new file mode 100644
index 000000000..a80fca2e7
--- /dev/null
+++ b/actix-http/benches/content-length.rs
@@ -0,0 +1,279 @@
+use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion};
+
+use bytes::BytesMut;
+
+// benchmark sending all requests at the same time
+fn bench_write_content_length(c: &mut Criterion) {
+    let mut group = c.benchmark_group("write_content_length");
+
+    let sizes = [
+        0, 1, 11, 83, 101, 653, 1001, 6323, 10001, 56329, 100001, 123456, 98724245,
+        4294967202,
+    ];
+
+    for i in sizes.iter() {
+        group.bench_with_input(BenchmarkId::new("Original (unsafe)", i), i, |b, &i| {
+            b.iter(|| {
+                let mut b = BytesMut::with_capacity(35);
+                _original::write_content_length(i, &mut b)
+            })
+        });
+
+        group.bench_with_input(BenchmarkId::new("New (safe)", i), i, |b, &i| {
+            b.iter(|| {
+                let mut b = BytesMut::with_capacity(35);
+                _new::write_content_length(i, &mut b)
+            })
+        });
+    }
+
+    group.finish();
+}
+
+criterion_group!(benches, bench_write_content_length);
+criterion_main!(benches);
+
+mod _new {
+    use std::{ptr, slice};
+
+    use bytes::{BufMut, BytesMut};
+
+    const DEC_DIGITS_LUT: &[u8] = b"0001020304050607080910111213141516171819\
+          2021222324252627282930313233343536373839\
+          4041424344454647484950515253545556575859\
+          6061626364656667686970717273747576777879\
+          8081828384858687888990919293949596979899";
+
+    const DIGITS_START: u8 = b'0';
+
+    /// NOTE: bytes object has to contain enough space
+    pub fn write_content_length(n: usize, bytes: &mut BytesMut) {
+        if n == 0 {
+            bytes.put_slice(b"\r\ncontent-length: 0\r\n");
+            return;
+        }
+
+        bytes.put_slice(b"\r\ncontent-length: ");
+
+        if n < 10 {
+            bytes.put_u8(DIGITS_START + (n as u8));
+        } else if n < 100 {
+            let n = n as u8;
+
+            let d10 = n / 10;
+            let d1 = n % 10;
+
+            bytes.put_u8(DIGITS_START + d10);
+            bytes.put_u8(DIGITS_START + d1);
+        } else if n < 1000 {
+            let n = n as u16;
+
+            let d100 = (n / 100) as u8;
+            let d10 = ((n / 10) % 10) as u8;
+            let d1 = (n % 10) as u8;
+
+            bytes.put_u8(DIGITS_START + d100);
+            bytes.put_u8(DIGITS_START + d10);
+            bytes.put_u8(DIGITS_START + d1);
+        } else if n < 10000 {
+            let n = n as u16;
+
+            let d1000 = (n / 1000) as u8;
+            let d100 = ((n / 100) % 10) as u8;
+            let d10 = ((n / 10) % 10) as u8;
+            let d1 = (n % 10) as u8;
+
+            bytes.put_u8(DIGITS_START + d1000);
+            bytes.put_u8(DIGITS_START + d100);
+            bytes.put_u8(DIGITS_START + d10);
+            bytes.put_u8(DIGITS_START + d1);
+        } else {
+            write_usize(n, bytes);
+        }
+
+        bytes.put_slice(b"\r\n");
+    }
+
+    pub(crate) fn write_usize(mut n: usize, bytes: &mut BytesMut) {
+        let mut curr: isize = 39;
+        let mut buf = [0u8; 39];
+
+        let buf_ptr = buf.as_mut_ptr();
+        let lut_ptr = DEC_DIGITS_LUT.as_ptr();
+
+        // eagerly decode 4 characters at a time
+        while n >= 10_000 {
+            let rem = (n % 10_000) as isize;
+            n /= 10_000;
+
+            let d1 = (rem / 100) << 1;
+            let d2 = (rem % 100) << 1;
+            curr -= 4;
+            unsafe {
+                ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+                ptr::copy_nonoverlapping(
+                    lut_ptr.offset(d2),
+                    buf_ptr.offset(curr + 2),
+                    2,
+                );
+            }
+        }
+
+        // if we reach here numbers are <= 9999, so at most 4 chars long
+        let mut n = n as isize; // possibly reduce 64bit math
+
+        // decode 2 more chars, if > 2 chars
+        if n >= 100 {
+            let d1 = (n % 100) << 1;
+            n /= 100;
+            curr -= 2;
+            unsafe {
+                ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+            }
+        }
+
+        // decode last 1 or 2 chars
+        if n < 10 {
+            curr -= 1;
+            unsafe {
+                *buf_ptr.offset(curr) = (n as u8) + b'0';
+            }
+        } else {
+            let d1 = n << 1;
+            curr -= 2;
+            unsafe {
+                ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+            }
+        }
+
+        unsafe {
+            bytes.extend_from_slice(slice::from_raw_parts(
+                buf_ptr.offset(curr),
+                39 - curr as usize,
+            ));
+        }
+    }
+}
+
+mod _original {
+    use std::{mem, ptr, slice};
+
+    use bytes::{BufMut, BytesMut};
+
+    const DEC_DIGITS_LUT: &[u8] = b"0001020304050607080910111213141516171819\
+          2021222324252627282930313233343536373839\
+          4041424344454647484950515253545556575859\
+          6061626364656667686970717273747576777879\
+          8081828384858687888990919293949596979899";
+
+    /// NOTE: bytes object has to contain enough space
+    pub fn write_content_length(mut n: usize, bytes: &mut BytesMut) {
+        if n < 10 {
+            let mut buf: [u8; 21] = [
+                b'\r', b'\n', b'c', b'o', b'n', b't', b'e', b'n', b't', b'-', b'l',
+                b'e', b'n', b'g', b't', b'h', b':', b' ', b'0', b'\r', b'\n',
+            ];
+            buf[18] = (n as u8) + b'0';
+            bytes.put_slice(&buf);
+        } else if n < 100 {
+            let mut buf: [u8; 22] = [
+                b'\r', b'\n', b'c', b'o', b'n', b't', b'e', b'n', b't', b'-', b'l',
+                b'e', b'n', b'g', b't', b'h', b':', b' ', b'0', b'0', b'\r', b'\n',
+            ];
+            let d1 = n << 1;
+            unsafe {
+                ptr::copy_nonoverlapping(
+                    DEC_DIGITS_LUT.as_ptr().add(d1),
+                    buf.as_mut_ptr().offset(18),
+                    2,
+                );
+            }
+            bytes.put_slice(&buf);
+        } else if n < 1000 {
+            let mut buf: [u8; 23] = [
+                b'\r', b'\n', b'c', b'o', b'n', b't', b'e', b'n', b't', b'-', b'l',
+                b'e', b'n', b'g', b't', b'h', b':', b' ', b'0', b'0', b'0', b'\r',
+                b'\n',
+            ];
+            // decode 2 more chars, if > 2 chars
+            let d1 = (n % 100) << 1;
+            n /= 100;
+            unsafe {
+                ptr::copy_nonoverlapping(
+                    DEC_DIGITS_LUT.as_ptr().add(d1),
+                    buf.as_mut_ptr().offset(19),
+                    2,
+                )
+            };
+
+            // decode last 1
+            buf[18] = (n as u8) + b'0';
+
+            bytes.put_slice(&buf);
+        } else {
+            bytes.put_slice(b"\r\ncontent-length: ");
+            convert_usize(n, bytes);
+        }
+    }
+
+    pub(crate) fn convert_usize(mut n: usize, bytes: &mut BytesMut) {
+        let mut curr: isize = 39;
+        let mut buf: [u8; 41] = unsafe { mem::MaybeUninit::uninit().assume_init() };
+        buf[39] = b'\r';
+        buf[40] = b'\n';
+        let buf_ptr = buf.as_mut_ptr();
+        let lut_ptr = DEC_DIGITS_LUT.as_ptr();
+
+        // eagerly decode 4 characters at a time
+        while n >= 10_000 {
+            let rem = (n % 10_000) as isize;
+            n /= 10_000;
+
+            let d1 = (rem / 100) << 1;
+            let d2 = (rem % 100) << 1;
+            curr -= 4;
+            unsafe {
+                ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+                ptr::copy_nonoverlapping(
+                    lut_ptr.offset(d2),
+                    buf_ptr.offset(curr + 2),
+                    2,
+                );
+            }
+        }
+
+        // if we reach here numbers are <= 9999, so at most 4 chars long
+        let mut n = n as isize; // possibly reduce 64bit math
+
+        // decode 2 more chars, if > 2 chars
+        if n >= 100 {
+            let d1 = (n % 100) << 1;
+            n /= 100;
+            curr -= 2;
+            unsafe {
+                ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+            }
+        }
+
+        // decode last 1 or 2 chars
+        if n < 10 {
+            curr -= 1;
+            unsafe {
+                *buf_ptr.offset(curr) = (n as u8) + b'0';
+            }
+        } else {
+            let d1 = n << 1;
+            curr -= 2;
+            unsafe {
+                ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
+            }
+        }
+
+        unsafe {
+            bytes.extend_from_slice(slice::from_raw_parts(
+                buf_ptr.offset(curr),
+                41 - curr as usize,
+            ));
+        }
+    }
+}