# COSRX Vitamin C 23 vs Sunday Riley C.E.O. 15%: Which to Choose?

**Question answered:** What is the difference between COSRX Vitamin C 23 Serum and Sunday Riley C.E.O. 15% Vitamin C Serum?

Published 2026-10-13, updated 2026-10-13. Data is taken from manufacturer labels; the products have not been tested.

The main differences are the form of vitamin C and the scent ingredients. COSRX Advanced The Vitamin C 23 Serum lists ascorbic acid at 23% and no fragrance. Sunday Riley C.E.O. 15% lists tetrahexyldecyl ascorbate, an oil-soluble vitamin C derivative, at 15%, along with glycolic acid, orange and tangerine peel oils, linalool and limonene.

## How the labels differ

[COSRX Advanced The Vitamin C 23 Serum](/products/cosrx-advanced-the-vitamin-c-23-serum/) lists 30 ingredients. Its top five are water, ascorbic acid (23%), butylene glycol, dimethicone and panthenol. It also lists 3-O-ethyl ascorbic acid, caffeine, niacinamide, glutathione, tocotrienols and tocopherol. COSRX sells it as fragrance free, and the list contains no fragrance allergens. The bottle is 20 ml.

[Sunday Riley C.E.O. 15% Vitamin C Brightening Serum](/products/sunday-riley-c-e-o-15-vitamin-c-brightening-serum/) lists 27 ingredients. Its top five are water, tetrahexyldecyl ascorbate, [squalane](/ingredients/squalane/), polyglyceryl-6 distearate and PEG-8 beeswax. It also lists [glycolic acid](/ingredients/glycolic-acid/). It lists orange peel oil, tangerine peel oil, [linalool](/ingredients/linalool/) and [limonene](/ingredients/limonene/). The bottle is 30 ml.

Both use [vitamin C](/ingredients/vitamin-c/), but in different forms and at different stated percentages. Besides water, the labels share 2 ingredients, squalane and tocopherol. Neither product file names skin types.

| Product | Key ingredients | Skin types | Fragrance | Flagged ingredients | Size | Source | Buy |
| --- | --- | --- | --- | --- | --- | --- | --- |
| [COSRX Advanced The Vitamin C 23 Serum](https://dermalguide.com/products/cosrx-advanced-the-vitamin-c-23-serum/) | Ascorbic Acid (Vitamin C) 23% | Brand doesn't say | Sold as fragrance free | Nothing flagged | 20 ml | [Manufacturer label](https://www.cosrx.com/products/the-vitamin-c-23-serum), checked 2026-10-10 | [Amazon (affiliate)](https://amzn.to/4rYImhH) |
| [Sunday Riley C.E.O. 15% Vitamin C Brightening Serum](https://dermalguide.com/products/sunday-riley-c-e-o-15-vitamin-c-brightening-serum/) | Vitamin C (THD Ascorbate) 15% | Brand doesn't say | Scent ingredients on the label | Limonene, Linalool | 30 ml | [Manufacturer label](https://sundayriley.com/products/ceo-vitamin-c-brightening-serum), checked 2026-10-10 | [Amazon (affiliate)](https://amzn.to/4e0IU0M) |

## Which to choose

Choose COSRX Advanced The Vitamin C 23 Serum if you want: Pure ascorbic acid, listed second at 23%; No citrus oils or fragrance allergens on the label.

Choose Sunday Riley C.E.O. 15% Vitamin C Brightening Serum if you want: Tetrahexyldecyl ascorbate, a vitamin C derivative; Glycolic acid in the same formula.


## Questions

### Which form of vitamin C does each one use?

COSRX lists ascorbic acid at 23%, plus 3-O-ethyl ascorbic acid. Sunday Riley C.E.O. lists tetrahexyldecyl ascorbate (THD ascorbate) at 15%.

### Which one lists fragrance ingredients?

C.E.O. 15% lists orange peel oil, tangerine peel oil, linalool and limonene. The COSRX Vitamin C 23 label lists no fragrance, citrus oils or fragrance allergens.

### Do they share ingredients?

Besides water, two ingredients appear on both labels: squalane and tocopherol.