What was the growth rate of service revenue in 4Q '20 
mall premium to organic build cost. We have a variety of M&A opportunities on our radar screen, some of which are sizable.
Turning to slide 15. A foundation of our strategy is to be a total solution provider to the leading Chinese customers, wherever they have critical mass of demand. Our customers see a lot of value in working with partner who understands their ecosystem. The same logic which takes us to new markets in China, leads us to look at expanding overseas.
Hong Kong is a start point outside mainland China. We currently have two major projects, the first of which is expected to come into service in 2022. We have recently secured anchor orders for Hong Kong 1 which we will announce in the next few months.
The China cloud and internet giants have big ambitions in South East Asia, both directly through their core platforms and indirectly through their strategic investments. Take AliCloud as an example, they already have three AZs in Singapore, two in Malaysia, and two in Indonesia. Singapore is a well-established hub for South East Asia and a Global Tier 1 data center market. In recent years, we believe that a large part of incremental demand in Singapore has come from our home market customers. For the time being, the Singapore government has suspended data center project approvals, while new policies are developed around land and power allocation. It is uncertain whether Singapore, given its resource constraints will choose to open the door wide for extensive hyperscale development.
The adjacent markets in Malaysia and Indonesia are less developed than Singapore but have high growth potential. We believe that Chinese customer demand will be a critical success factor in these countries as well. We have established a picture of demand from our home market customers. They have repeatedly requested us to establish a presence. We are actively pursuing opportunities with existing assets in Singapore, as well as getting positioned for when approvals restart. We have also entered into discussions with a number of potential local partners who have projects at various stages of development in Malaysia and Indonesia.
We believe that expansion into South East Asia is strategically important and that we can capture several hundred megawatts of new business over the next five years. We are moving ahead in a very careful and deliberate way. We aim to announce several new commitments in South East Asia over the course of this year.
To conclude my section, GDS is head and shoulders above everyone else in the China market. This is a matter of fact. With what I told you today about the market opportunity in front of us, our strategic positioning and our competitive advantages, we believe that the gap is only going to get bigger.
Now, I will hand over to Dan for the financial and operating review.
Dan Newman -- Chief Financial Officer
Thank you, William. Starting on slide 18 where we strip out the contribution from equipment sales and the effect of FX changes. In 4Q '20, our service revenue grew by 6.9%. Underlying adjusted gross profit grew by 7.5%. And underlying adjusted EBITDA grew by 6.2% quarter-on-quarter. Our underlying adjusted EBITDA margin was 46.8%.
Turning to slide 19. Service revenue growth is driven mainly by delivery of the committed backlog and closing of acquisitions. Net additional area utilized during 4Q '20 was 16,461 square meters, consistent with the previous two quarters.
The first quarter of each year is usually slower due to Chinese New Year. Nonetheless, we expect move-in in 1Q '21 to be only a couple of thousand square meters down on the prior quarters level. Given the timing of capacity increases, as shown on slide 23, we are forecasting move-in over the course of 2021 will be heavily weighted to the second half. Monthly service revenue, MSR declined 1.2% quarter-on-quarter in 4Q '20 to RMB2,489 per square meters per month.
As shown on the next slide, MSR for the whole of FY '20 was down 3.4% compared with FY '19. In FY '21, we expect a further low single digit decline. To some extent MSR is a reflection
mall premium to organic build cost. We have a variety of M&A opportunities on our radar screen, some of which are sizable.
Turning to slide 15. A foundation of our strategy is to be a total solution provider to the leading Chinese customers, wherever they have critical mass of demand. Our customers see a lot of value in working with partner who understands their ecosystem. The same logic which takes us to new markets in China, leads us to look at expanding overseas.
Hong Kong is a start point outside mainland China. We currently have two major projects, the first of which is expected to come into service in 2022. We have recently secured anchor orders for Hong Kong 1 which we will announce in the next few months.
The China cloud and internet giants have big ambitions in South East Asia, both directly through their core platforms and indirectly through their strategic investments. Take AliCloud as an example, they already have three AZs in Singapore, two in Malaysia, and two in Indonesia. Singapore is a well-established hub for South East Asia and a Global Tier 1 data center market. In recent years, we believe that a large part of incremental demand in Singapore has come from our home market customers. For the time being, the Singapore government has suspended data center project approvals, while new policies are developed around land and power allocation. It is uncertain whether Singapore, given its resource constraints will choose to open the door wide for extensive hyperscale development.
The adjacent markets in Malaysia and Indonesia are less developed than Singapore but have high growth potential. We believe that Chinese customer demand will be a critical success factor in these countries as well. We have established a picture of demand from our home market customers. They have repeatedly requested us to establish a presence. We are actively pursuing opportunities with existing assets in Singapore, as well as getting positioned for when approvals restart. We have also entered into discussions with a number of potential local partners who have projects at various stages of development in Malaysia and Indonesia.
We believe that expansion into South East Asia is strategically important and that we can capture several hundred megawatts of new business over the next five years. We are moving ahead in a very careful and deliberate way. We aim to announce several new commitments in South East Asia over the course of this year.
 To conclude my section, GDS is head and shoulders above everyone else in the China market. This is a matter of fact. With what I told you today about the market opportunity in front of us, our strategic positioning and our competitive advantages, we believe that the gap is only going to get bigger.
Now, I will hand over to Dan for the financial and operating review.
Dan Newman -- Chief Financial Officer
Thank you, William. Starting on slide 18 where we strip out the contribution from equipment sales and the effect of FX changes. In 4Q '20, our service revenue grew by 6.9%. Underlying adjusted gross profit grew by 7.5%. And underlying adjusted EBITDA grew by 6.2% quarter-on-quarter. Our underlying adjusted EBITDA margin was 46.8%.
Turning to slide 19. Service revenue growth is driven mainly by delivery of the committed backlog and closing of acquisitions. Net additional area utilized during 4Q '20 was 16,461 square meters, consistent with the previous two quarters.
The first quarter of each year is usually slower due to Chinese New Year. Nonetheless, we expect move-in in 1Q '21 to be only a couple of thousand square meters down on the prior quarters level. Given the timing of capacity increases, as shown on slide 23, we are forecasting move-in over the course of 2021 will be heavily weighted to the second half. Monthly service revenue, MSR declined 1.2% quarter-on-quarter in 4Q '20 to RMB2,489 per square meters per month.
As shown on the next slide, MSR for the whole of FY '20 was down 3.4% compared with FY '19. In FY '21, we expect a further low single digit decline. To some extent MSR is a reflection