slack.com

Readiness by lane

Green: slack.com. Thin bar: Workplace Productivity peer median.

Priority fixes for slack.com

Ordered by impact and by how common each practice is among peers.

1. Priority 1 · Accelerate

   Modern image formats in use

   Observed: The homepage had 89 images and none used WebP or AVIF.

   Why it matters: WebP and AVIF are typically much smaller than JPEG or PNG at similar quality, and images are often the heaviest part of a page.

   What to do: Serve WebP or AVIF with a JPEG or PNG fallback, either through an image CDN or by generating both formats at build time.

   49% of Workplace Productivity peers do this. Limit: Based on the homepage HTML delivered to an automated client; scripts that run later were not executed.

   Guide: AVIF, WebP, JPEG, and PNG: Choose the Right Image Format

2. Priority 2 · Accelerate

   No render-blocking scripts in <head>

   Observed: The homepage <head> loaded 3 external scripts without async or defer.

   What to do: Add defer to scripts that need the DOM, async to independent ones such as analytics, or move them to the end of the body.

   42% of Workplace Productivity peers do this.

   Guide: Control Third-Party Scripts Before They Control Your Page

3. Priority 3 · Harden

   Content Security Policy present

   Observed: The homepage response did not include a Content-Security-Policy header.

   What to do: Start with Content-Security-Policy-Report-Only to see what would break, tighten the policy over a few weeks, then enforce it.

   41% of Workplace Productivity peers do this.

   Guide: Payment Security and PCI DSS: What Website Owners Need to Know

4. Priority 4 · Harden

   X-Content-Type-Options: nosniff

   Observed: The homepage response did not include X-Content-Type-Options: nosniff.

   What to do: Send X-Content-Type-Options: nosniff on all responses and make sure each file is served with the correct Content-Type.

   51% of Workplace Productivity peers do this.

   Guide: A Practical Website Health Check for Owners

What slack.com already does well

Practices fewer than half of Workplace Productivity peers use.

• DNSSEC signedDNSSEC delegation (DS record) present.12% of peers
• security.txt publishedsecurity.txt with a contact found.16% of peers
• CAA records limit who can issue certificatesCAA limits issuance to digicert.com, letsencrypt.org.18% of peers

What we saw

Homepage checked

https://slack.com/

Homepage response

HTTP 200

TLS

TLSv1.3, HTTP/2

Certificate

Let's Encrypt, 89-day validity, expiring 2027-01-05

DNS operators

Amazon Route 53

HSTS

max-age 365 days, includeSubDomains, preload

DMARC policy

p=reject

Homepage HTML

247 KB, br

Images on homepage

89 (png 65, svg 20, jpg 10)

Limits: homepage only, one location, one moment. Header checks reflect the homepage response; other pages may differ.

Stack and providers

Seen in the homepage response, certificate and DNS. Provider pages compare how their customers configure the same checks.

All 31 checks

Select a gap for the method and fix. How each check works

Compare with other Workplace Productivity sites

• asana.com81
• atlassian.com84
• miro.com87
• notion.com84
• wrike.com82

Workplace Productivity readiness benchmark