Step 3 of 4 in Level 2: Make your first post

Edit slides, captions and alt text

Change the words on any slide, add or reorder slides, write the caption and add alt text, so people who use a screen reader know what each image shows.

About 5 minutes 6 steps Updated

Short answer

To edit a post in Blackbox (blackbox.plus), open it from the Library tab in Studio and click Edit slide on the preview. Click the words on a slide and type; a slide fits a 70-character headline and 35 words in all, and it saves when you click away. Rewrite with AI offers new versions and changes nothing until you pick one. In the strip of slides you can drag to reorder, add, duplicate or delete, keeping a carousel between 2 and 10 slides, and Undo or History brings back any change. Under Alt text, describe what each slide shows, up to 1,000 characters; Blackbox sends it to Instagram with each picture so screen readers can read it aloud. Then open step 1, Caption, and write it yourself or click Write it for me. One caption goes to every account you post to. A scheduled post is locked, so unschedule it first to make changes.

Before you start

A post or carousel in Studio

Made from an idea or uploaded. Open it from the Library tab in Studio. See Make an Instagram carousel with AI.

Not scheduled yet

A scheduled post is locked so what goes out is what you checked. Click Unschedule on its Post step first if you need to change it.

How to edit slides, captions and alt text in Blackbox

  1. 01

    Open the slide editor

    On the post, click Edit slide on the preview. The editor opens on that slide; the arrow keys move between slides.

  2. 02

    Change the words

    Click the words on the slide and type. A slide fits a 70-character headline and 35 words in all, and a counter shows where you are. It saves when you click away. To have them rewritten, add a note under Anything to aim for? (say, "mention the price"), click Rewrite with AI and pick the version you like — nothing changes until you do.

  3. 03

    Arrange the slides

    In the strip of slides, drag to reorder, or use + Add, Duplicate and Delete. Under Layout, move the words to the Top, Middle or Bottom, or make the headline Smaller or Larger. Every change saves on its own; Undo and History bring back anything.

  4. 04

    Add alt text

    Under Alt text, describe what the slide shows, as you would to someone who cannot see it — up to 1,000 characters. Blackbox sends it to Instagram with each picture. Click Done when you are finished.

  5. 05

    Write the caption

    Back on the post, open step 1, Caption. Write it yourself, or click Write it for me for a draft from the topic. It saves when you click away.

  6. 06

    Check it

    Open step 2, Check. It lists what is left: the caption, slides still drawing, and any slide without alt text. Missing alt text is a reminder, not a blocker.

Good to know

  • One caption goes to every account you post to — there is no separate caption per platform.
  • There is no Save button: each change saves on its own, and History keeps the version before every edit.
  • With your own uploaded pictures, the editor reorders and deletes them; it does not change the pictures themselves.
  • A carousel holds 2 to 10 slides.

Questions people ask

How do I write a good Instagram caption?
Put the point in the first line — Instagram shows only the start of a caption until someone taps more. Say one thing, in the words your customers use, and end on what to do next. Studio’s draft already ends on your brand’s ask; edit it until it sounds like you.
What is alt text, and do I need it?
A short description of an image that screen readers read aloud to people who cannot see it. Instagram uses it for that, and Blackbox sends what you write with each picture. You can post without it, but it takes a minute and makes the post usable by everyone.
Can I write different captions for Instagram and TikTok?
Not today — one caption goes everywhere. TikTok shows the caption’s first line, without hashtags, as the title of a photo post, so make that first line work on its own.
It says Not saved
The words did not fit the slide: a headline is required, it fits 70 characters, and a slide fits 35 words. The message says how much to cut.
I changed something by mistake
Click Undo (or press ⌘Z). For anything older, open History and click Restore next to the version you want.

Stuck at any step? Send us a message and we'll do it with you on a call. All of Level 2: Make your first post