diff --git a/Marlin/src/HAL/HAL_AVR/math_AVR.h b/Marlin/src/HAL/HAL_AVR/math_AVR.h
index e84e5bb79b..64c9c7998e 100644
--- a/Marlin/src/HAL/HAL_AVR/math_AVR.h
+++ b/Marlin/src/HAL/HAL_AVR/math_AVR.h
@@ -36,9 +36,9 @@
 // D C B A is longIn2
 //
 static FORCE_INLINE uint16_t MultiU24X32toH16(uint32_t longIn1, uint32_t longIn2) {
-  register uint8_t tmp1;
-  register uint8_t tmp2;
-  register uint16_t intRes;
+  uint8_t tmp1;
+  uint8_t tmp2;
+  uint16_t intRes;
   __asm__ __volatile__(
     A("clr %[tmp1]")
     A("mul %A[longIn1], %B[longIn2]")
@@ -90,8 +90,8 @@ static FORCE_INLINE uint16_t MultiU24X32toH16(uint32_t longIn1, uint32_t longIn2
 // r26 to store 0
 // r27 to store the byte 1 of the 24 bit result
 static FORCE_INLINE uint16_t MultiU16X8toH16(uint8_t charIn1, uint16_t intIn2) {
-  register uint8_t tmp;
-  register uint16_t intRes;
+  uint8_t tmp;
+  uint16_t intRes;
   __asm__ __volatile__ (
     A("clr %[tmp]")
     A("mul %[charIn1], %B[intIn2]")
diff --git a/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp b/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp
index a333e2e350..b127f1a990 100644
--- a/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp
+++ b/Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp
@@ -78,11 +78,11 @@
 
   // run at ~8 .. ~10Mhz - Tx version (Rx data discarded)
   static uint8_t spiTransferTx0(uint8_t bout) { // using Mode 0
-    register uint32_t MOSI_PORT_PLUS30 = ((uint32_t) PORT(MOSI_PIN)) + 0x30;  /* SODR of port */
-    register uint32_t MOSI_MASK = PIN_MASK(MOSI_PIN);
-    register uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
-    register uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
-    register uint32_t idx = 0;
+    uint32_t MOSI_PORT_PLUS30 = ((uint32_t) PORT(MOSI_PIN)) + 0x30;  /* SODR of port */
+    uint32_t MOSI_MASK = PIN_MASK(MOSI_PIN);
+    uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
+    uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
+    uint32_t idx = 0;
 
     /* Negate bout, as the assembler requires a negated value */
     bout = ~bout;
@@ -161,11 +161,11 @@
 
   // run at ~8 .. ~10Mhz - Rx version (Tx line not altered)
   static uint8_t spiTransferRx0(uint8_t bout) { // using Mode 0
-    register uint32_t bin = 0;
-    register uint32_t work = 0;
-    register uint32_t BITBAND_MISO_PORT = BITBAND_ADDRESS( ((uint32_t)PORT(MISO_PIN))+0x3C, PIN_SHIFT(MISO_PIN));  /* PDSR of port in bitband area */
-    register uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
-    register uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
+    uint32_t bin = 0;
+    uint32_t work = 0;
+    uint32_t BITBAND_MISO_PORT = BITBAND_ADDRESS( ((uint32_t)PORT(MISO_PIN))+0x3C, PIN_SHIFT(MISO_PIN));  /* PDSR of port in bitband area */
+    uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
+    uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
     UNUSED(bout);
 
     /* The software SPI routine */
@@ -281,12 +281,12 @@
 
   // Block transfers run at ~8 .. ~10Mhz - Tx version (Rx data discarded)
   static void spiTxBlock0(const uint8_t* ptr, uint32_t todo) {
-    register uint32_t MOSI_PORT_PLUS30 = ((uint32_t) PORT(MOSI_PIN)) + 0x30;  /* SODR of port */
-    register uint32_t MOSI_MASK = PIN_MASK(MOSI_PIN);
-    register uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
-    register uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
-    register uint32_t work = 0;
-    register uint32_t txval = 0;
+    uint32_t MOSI_PORT_PLUS30 = ((uint32_t) PORT(MOSI_PIN)) + 0x30;  /* SODR of port */
+    uint32_t MOSI_MASK = PIN_MASK(MOSI_PIN);
+    uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
+    uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
+    uint32_t work = 0;
+    uint32_t txval = 0;
 
     /* The software SPI routine */
     __asm__ __volatile__(
@@ -360,11 +360,11 @@
   }
 
   static void spiRxBlock0(uint8_t* ptr, uint32_t todo) {
-    register uint32_t bin = 0;
-    register uint32_t work = 0;
-    register uint32_t BITBAND_MISO_PORT = BITBAND_ADDRESS( ((uint32_t)PORT(MISO_PIN))+0x3C, PIN_SHIFT(MISO_PIN));  /* PDSR of port in bitband area */
-    register uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
-    register uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
+    uint32_t bin = 0;
+    uint32_t work = 0;
+    uint32_t BITBAND_MISO_PORT = BITBAND_ADDRESS( ((uint32_t)PORT(MISO_PIN))+0x3C, PIN_SHIFT(MISO_PIN));  /* PDSR of port in bitband area */
+    uint32_t SCK_PORT_PLUS30 = ((uint32_t) PORT(SCK_PIN)) + 0x30;    /* SODR of port */
+    uint32_t SCK_MASK = PIN_MASK(SCK_PIN);
 
     /* The software SPI routine */
     __asm__ __volatile__(
diff --git a/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_hw_i2c.cpp b/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_hw_i2c.cpp
index c71bb4ba6a..cf6284bdf2 100644
--- a/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_hw_i2c.cpp
+++ b/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_hw_i2c.cpp
@@ -156,7 +156,7 @@ uint8_t u8g_com_HAL_LPC1768_ssd_hw_i2c_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_v
          return 0;
         }
 
-        register uint8_t *ptr = (uint8_t *)arg_ptr;
+        uint8_t *ptr = (uint8_t *)arg_ptr;
         while (arg_val > 0) {
           if (u8g_i2c_send_byte(*ptr++) == 0) {
             u8g_i2c_stop();
@@ -175,7 +175,7 @@ uint8_t u8g_com_HAL_LPC1768_ssd_hw_i2c_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_v
           return 0;
         }
 
-        register uint8_t *ptr = (uint8_t *)arg_ptr;
+        uint8_t *ptr = (uint8_t *)arg_ptr;
         while (arg_val > 0) {
           if (u8g_i2c_send_byte(u8g_pgm_read(ptr)) == 0)
             return 0;
diff --git a/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_sw_i2c.cpp  under construction b/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_sw_i2c.cpp  under construction
index a0fd991654..80eeb50a8c 100644
--- a/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_sw_i2c.cpp  under construction	
+++ b/Marlin/src/HAL/HAL_LPC1768/u8g/u8g_com_HAL_LPC1768_ssd_sw_i2c.cpp  under construction	
@@ -214,7 +214,7 @@ uint8_t u8g_com_HAL_LPC1768_ssd_sw_i2c_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_v
       if (u8g_com_ssd_I2C_start_sequence_sw(u8g) == 0)
         return u8g_i2c_stop_sw(), 0;
 
-        register uint8_t *ptr = (uint8_t *)arg_ptr;
+        uint8_t *ptr = (uint8_t *)arg_ptr;
         while (arg_val > 0) {
           if (u8g_i2c_send_byte_sw(*ptr++) == 0)
             return u8g_i2c_stop_sw(), 0;
@@ -229,7 +229,7 @@ uint8_t u8g_com_HAL_LPC1768_ssd_sw_i2c_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_v
       if (u8g_com_ssd_I2C_start_sequence_sw(u8g) == 0)
         return u8g_i2c_stop_sw(), 0;
 
-        register uint8_t *ptr = (uint8_t *)arg_ptr;
+        uint8_t *ptr = (uint8_t *)arg_ptr;
         while (arg_val > 0) {
           if (u8g_i2c_send_byte_sw(u8g_pgm_read(ptr)) == 0) return 0;
           ptr++;
diff --git a/Marlin/src/module/planner.cpp b/Marlin/src/module/planner.cpp
index 6181528c03..c185678ad0 100644
--- a/Marlin/src/module/planner.cpp
+++ b/Marlin/src/module/planner.cpp
@@ -355,11 +355,11 @@ void Planner::init() {
       // For small divisors, it is best to directly retrieve the results
       if (d <= 110) return pgm_read_dword(&small_inv_tab[d]);
 
-      register uint8_t r8 = d & 0xFF,
-                       r9 = (d >> 8) & 0xFF,
-                       r10 = (d >> 16) & 0xFF,
-                       r2,r3,r4,r5,r6,r7,r11,r12,r13,r14,r15,r16,r17,r18;
-      register const uint8_t* ptab = inv_tab;
+      uint8_t r8 = d & 0xFF,
+              r9 = (d >> 8) & 0xFF,
+              r10 = (d >> 16) & 0xFF,
+              r2,r3,r4,r5,r6,r7,r11,r12,r13,r14,r15,r16,r17,r18;
+      const uint8_t* ptab = inv_tab;
 
       __asm__ __volatile__(
         // %8:%7:%6 = interval
diff --git a/Marlin/src/module/stepper.cpp b/Marlin/src/module/stepper.cpp
index 6a1beec94c..f86b514798 100644
--- a/Marlin/src/module/stepper.cpp
+++ b/Marlin/src/module/stepper.cpp
@@ -498,14 +498,14 @@ void Stepper::set_directions() {
    *        rhi = int32_t((mul >> 32) & 0xFFFFFFFF);
    *      }
    *      int32_t _eval_bezier_curve_arm(uint32_t curr_step) {
-   *        register uint32_t flo = 0;
-   *        register uint32_t fhi = bezier_AV * curr_step;
-   *        register uint32_t t = fhi;
-   *        register int32_t alo = bezier_F;
-   *        register int32_t ahi = 0;
-   *        register int32_t A = bezier_A;
-   *        register int32_t B = bezier_B;
-   *        register int32_t C = bezier_C;
+   *        uint32_t flo = 0;
+   *        uint32_t fhi = bezier_AV * curr_step;
+   *        uint32_t t = fhi;
+   *        int32_t alo = bezier_F;
+   *        int32_t ahi = 0;
+   *        int32_t A = bezier_A;
+   *        int32_t B = bezier_B;
+   *        int32_t C = bezier_C;
    *
    *        lsrs(ahi, alo, 1);          // a  = F << 31
    *        lsls(alo, alo, 31);         //
@@ -630,13 +630,13 @@ void Stepper::set_directions() {
       bezier_AV = av;
 
       // Calculate the rest of the coefficients
-      register uint8_t r2 = v0 & 0xFF;
-      register uint8_t r3 = (v0 >> 8) & 0xFF;
-      register uint8_t r12 = (v0 >> 16) & 0xFF;
-      register uint8_t r5 = v1 & 0xFF;
-      register uint8_t r6 = (v1 >> 8) & 0xFF;
-      register uint8_t r7 = (v1 >> 16) & 0xFF;
-      register uint8_t r4,r8,r9,r10,r11;
+      uint8_t r2 = v0 & 0xFF;
+      uint8_t r3 = (v0 >> 8) & 0xFF;
+      uint8_t r12 = (v0 >> 16) & 0xFF;
+      uint8_t r5 = v1 & 0xFF;
+      uint8_t r6 = (v1 >> 8) & 0xFF;
+      uint8_t r7 = (v1 >> 16) & 0xFF;
+      uint8_t r4,r8,r9,r10,r11;
 
       __asm__ __volatile__(
         /* Calculate the Bézier coefficients */
@@ -732,11 +732,11 @@ void Stepper::set_directions() {
       if (!curr_step)
         return bezier_F;
 
-      register uint8_t r0 = 0; /* Zero register */
-      register uint8_t r2 = (curr_step) & 0xFF;
-      register uint8_t r3 = (curr_step >> 8) & 0xFF;
-      register uint8_t r4 = (curr_step >> 16) & 0xFF;
-      register uint8_t r1,r5,r6,r7,r8,r9,r10,r11; /* Temporary registers */
+      uint8_t r0 = 0; /* Zero register */
+      uint8_t r2 = (curr_step) & 0xFF;
+      uint8_t r3 = (curr_step >> 8) & 0xFF;
+      uint8_t r4 = (curr_step >> 16) & 0xFF;
+      uint8_t r1,r5,r6,r7,r8,r9,r10,r11; /* Temporary registers */
 
       __asm__ __volatile(
         /* umul24x24to16hi(t, bezier_AV, curr_step);  t: Range 0 - 1^16 = 16 bits*/
@@ -1127,14 +1127,14 @@ void Stepper::set_directions() {
       #if defined(__ARM__) || defined(__thumb__)
 
         // For ARM Cortex M3/M4 CPUs, we have the optimized assembler version, that takes 43 cycles to execute
-        register uint32_t flo = 0;
-        register uint32_t fhi = bezier_AV * curr_step;
-        register uint32_t t = fhi;
-        register int32_t alo = bezier_F;
-        register int32_t ahi = 0;
-        register int32_t A = bezier_A;
-        register int32_t B = bezier_B;
-        register int32_t C = bezier_C;
+        uint32_t flo = 0;
+        uint32_t fhi = bezier_AV * curr_step;
+        uint32_t t = fhi;
+        int32_t alo = bezier_F;
+        int32_t ahi = 0;
+        int32_t A = bezier_A;
+        int32_t B = bezier_B;
+        int32_t C = bezier_C;
 
          __asm__ __volatile__(
           ".syntax unified" "\n\t"              // is to prevent CM0,CM1 non-unified syntax