Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 12, 2021
Cover [Abstract]
Entity Registrant Name	Clearside Biomedical, Inc.
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Trading Symbol	CLSD
Document Type	10-Q
Entity Central Index Key	0001539029
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Interactive Data Current	Yes
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Entity Common Stock, Shares Outstanding		57,578,725
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity File Number	001-37783
Entity Tax Identification Number	45-2437375
Entity Address, Address Line One	900 North Point Parkway
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	Alpharetta
Entity Address, State or Province	GA
Entity Address, Postal Zip Code	30005
City Area Code	678
Local Phone Number	270-3631